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srrata 
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1 

2 

3 

1 

2 

3 

4 

5 

6 

AN    t:XAMINAT10N 


OF 


WEISMANNISM 


■Hiiiiiiiii 


mmmmmmm 


AN   ILXAMINATION 


» J  •'  >  ' 

«•  *•• 

•    •     • 

4>  «  ar 


OF 


WEISMANNISM 


BY 


(JKOKdK   JOHN    KOMANKS,  M.A.,  I.I.D..  K.R.S. 

IIONOKAKV  FELLOW  or  (iONVII.LK  AND  CAIIIS  (  o|  l.h'liR, 
CAMIIKIIM.K 


« 

J  il   J  4  • 
I)  li  <1« 

•:  >": 

l>  J    ,•» 


CHICAGO 
TIIK  OI'EN  COURT  I'UHl.ISHING  COMPANY 


n 


•  • . , , 


<  •  •  •  t 

•  •  t , 

•  I  >  a  r 

( 

•  •  I  I  I 


Qw  ^- \  :^-i. 


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'.  It 

• « 

<  •  I  •  I 


••til 

•  •  •  > , 

•  • « I . 
.« •  ♦  • 


PUBLISHERS  NOTE. 


'   4   ,^ 


I 

I       • 

■<■'%* 


Several  parts  of  this  book,  especially  the  article  in  rh,„* 


^ 


\^ 


CONTENTS 


CHAP. 


% 


.« 


^ 


I.    STATKNfKNT     OF      WkIsMANN's     SysTFM      r 

Year  issr.  . 


PACE 


P      TO      THE 


II.     LATr       ADDITIONS    TO   WeisMANN's  Sv.sTEM    UP  To    ,  „, 
YEAR    l8y2     . 


28 


W.I'TION 


III.  Weismann's  Theory  of  IlEREniTY  (1S9,)    .        .        .        s 

IV.  KXAMINATION   OF  WeISMANNS   TllEOkV   OF    !■  V. 

('890 

•  •  •  . 

V.    WeISMANNISM   irp  TO   nATE(lSy.3)  . 

Appendix  I._On  Germ-pi.asm 

*        •        •       • 

..         II.— On  Tei.egony  . 


86 
117 

191 


o>flr:r^rQ 


21 


't^i'w*..  •-> 


\ 


n 


'  ! 


•  t  •  1 ,    1 


•  •  ♦  • » 
.  •  * 


" « • » 

•  •  •  i  > 

.  •  •    ■ 

*  •  •  • 


<  •  •  •  a 
•  a 


.  a  •  ' 


'  •  »  a  • 
'  •  a  .  , 


■  «  a  a 

>  <  I  a 


n  a  ( 


'   t  t  Ht 


•        I 

>   •  t    • 


PRHl^\Cli 


As  alrPHfly   stated   in   the   Preface  to   the   second 
edition  of  Darwin  and  after  Darwin.  Part   I,  seven 
and  protracted  illness  has  hitherto  prevented  me  from 
proceeding  to  the  puuh'cation  of  Part  11.     It  is  now 
more  than       year  since   I   had  to  suspend  work  of 
every    kind,    and   therefore,    althoiijrh    at    that    time 
Part  II  was  almost  ready  for  press,  I  have  not  yet  been 
able  to  write  its  concluding  chai)tcrs.     Shortly  before 
and    during   this    interval    Professor    Weisniann    has 
produced  his  essays  on  Amthiviixis  and  The  Gervi- 
plasm.     These  works  present  extensive  additions  to, 
and  considerable  modifications  of,  his  previous  theories 
as  collected  together  in  the  English  translation,  under 
the  title  Essays  on  Heredity,  VoL  I.     Consequently, 
it  has  become  necessary  for  me  either  to  re-write  the 
examination  of  his  system  which  I  had  prepared  for 
Part  II  of  my  own   treatise,  or   else  to    leave  that 
examination  as  it  stood,  and  to  add  a  further  chapter 
dealing  with  those  later  devcloi)ments  of  his  system 
to  which  I  have  just  alluded.     After  due  reflection 


■? 


', ... 


'  •  «  t  • 


f    •   t  f  r 


*  .      •  • 

c    1    .    •    , 


c  C  ft  •  • 
'  «  e  .  , 


•  <  •  I 
\  •  •   t 


i     1 


VI 


Preface. 


I  have  decided  ipon  the  latter  course,  because  in  this 
way  we  arc  most  likely  to  obtain  a  clear  view  of  the 
growth  of  Wcismann's  elaborate  structure  of  theories 
— a  view  which  it  is  almost  necessary,  for  the  purposes 
of  criticism,  that  we  should  obtain. 

Having  decided  upon  this  point,  it  occurred  to  me 
that  certain  advantai^cs  would  be  gained  by  removing 
the  whole  criticism  from  the  position  which  it  was 
originally  intended  to  occupy  as  a  section  of  my 
forthcoming  volume  on  the  Post-Darwinian  period. 
For,  in  con.-equcncc  of  the  criticism  having  been 
written  at  successive  intervals  during  the  last  six  or 
eight  years  as  Professor  VVeismann's  works  succes- 
sively appeared,  it  has  now  swelled  to  a  bulk  which 
would  unduly  encumber  the  volume  just  mentioned, 
i^gain,  the  growth  of  Professor  Wcismann's  system 
has  of  late  become  so  rapid,  that  if  the  criticism 
is  to  keep  pace  with  it  in  future,  the  best  plan 
will  doubtless  be  the  one  which  it  is  now  my 
intention  to  adopt — viz.,  to  publish  the  criticism  in 
a  separate  form,  and  in  comparatively  small  editions, 
so  that  further  chapters  may  be  added  with  as  much 
celerity  as  Professor  Wcismann  may  hereafter  pro- 
duce his  successive  works.  Lastly,  where  so  much 
elaborate  speculation  and  so  many  changes  of  doctrine 
are  concerned,  it  is  inevitable  that  some  misunder- 
standings on  the  part  of  a  critic  are  likely  to  have 
arisen  ;  and  therefore,  should  Professor  Wcismann 
deem  ic  worth  his  while  to  correct  any  such  failings 
on  my  part,  tlu;  pi  in  of  publication  just  alluded   to 


Pnface. 


Vll 


because  in  this 
lear  view  of  the 
ture  of  theories 
for  the  purposes 

occurred  to  me 
cd  by  removing 
1  which  it  was 
section  of  my 
rwinian  period, 
n    having   been 
the  last  six  or 
works  succcs- 
o  a  bulk  which 
just  mentioned. 
Imann's  system 
f  the  criticism 
the    best   plan 
t    is   now    my 
le  criticism  in 
mall  editions, 
with  as  much 
lercaftcr  pro- 
icre  so   much 
es  of  doctrine 
mc  misundcr- 
kcly  to  ha\e 
)r   Wcismann 
such  failings 
t  alluded   to 


will  furnish  mc  with  the  best  opportunity  of  dealing 
with  whatever  he  may  have  to  sa)-. 

It  must  be  understood,  however,  that  under  the 
term  '' W'eismannism ''  I  d()  not  inclutle  any  re'.creiice 
to  the  important  question  with  which  the  name  of 
Wcismann    has    been     mainly    associated — i.e.,    the 


of 


.d  ch 


ritance  or  non-uihcntance  ot  acquncd  characters. 

This  is  a  question  of  fact,  which  stands  to  be  an- 
swered by  the  inductive  methods  of  observation  and 
experiment:  not  by  the  deductive  methods  of  general 
reasoning.  Of  course  Professor  Wcismann  is  fully 
entitled  to  assume  a  negative  answer  as  a  basis 
whereon  to  construct  his  theory  of  the  continuity  of 
germ-plasm  ;  but  no  amount  of  speculation  as  to  what 
the  mechanism  of  heredity  is  likely  to  be  if  once  this 
assumption  is  granted,  can  even  so  much  as  tend  to 
prove  that  the  assumption  itself  is  true.  Therefore, 
in  this  "examination  of  Weismannism"'  I  intend  to 
restrict  our  attention  to  the  elaborate  system  of 
theories  which  Wcismann  has  reared  upon  his  funda- 
mental postulate  of  the  non-inheritance  of  acquired 
characters,  reserving  for  my  next  volume  our  con- 
sideration of  this  postulate  itself 

Lest,  however,  it  should  be  felt  that  "an  examina- 
tion of  Weismannism  "  m  which  the  question  of  the 
transmission  of  accpiired  characters  is  omitted  must 
indeed  i)rove  a  case  of  Hamlet  without  the  Prince  of 
Denmark,  I  may  be  allowed  to  make  two  observations. 
In  the  fust  place,  this  great  (juestion  of  fact  is  clearly 
quite  distinct  from  that  of  any  theories  which  may  be 


?r 


■  «  1 
'  >  >  •  < 


1  < » •  I 
■- « c  i , 

"  •   «  C  t 

I  "  *  e 


-  ^  «  •  f. 

■  V  i  t 

>      c 

t  »  '.  .• 


Vlll 


Prejace. 


framed  upon  cither  side  of  it.  And,  in  the  second 
place,  the  question  was  not  raised  by  Weismann.  It 
appears,  indeed,  from  what  he  says,  that  he  never 
caught  a  glimpse  of  it  till  about  ten  years  ago,  and 
that  he  then  did  so  as  a  result  of  his  own  indei)endent 
thought.  Moreover,  it  is  perfectly  true  that  to  him 
belongs  the  great  merit  of  having  been  the  first  to 
call  general  attention  to  the  subject,  and  so  to  arouse 
a  world-wide  interest  with  reference  to  it.  But  to 
suppose  that  the  question  was  first  propounded  by 
Weismann  is  merely  to  display  a  want  of  acquaint- 
ance with  the  course  of  Darwinian  thought  in  this 
country.  As  far  back  as  1874  I  had  long  conversa- 
tions with  Darwin  himself  upon  the  matter,  and  under 
his  guidance  performed  what  I  suppose  are  the  only 
systematic  experiments  which  have  ever  been  under- 
taken with  regard  to  it.  These  occupied  more  than 
five  years  of  almost  exclusive  devotion ;  but,  as 
they  all  proved  failures,  they  were  never  published. 
Therefore  I  here  mention  them  merely  for  the  pur- 
pose of  showing  that  the  idea  of  what  is  now  called 
a  "  coiitinuity  of  germ-plasm  "  was  present  to  Dar- 
win's mind  as  a  logically  possible  alternative  to  the 
one  which  he  adopted  in  his  theory  of  pangenesis — an 
alternative,  therefore,  which  he  was  anxious  to  ex- 
clude by  way  of  experimental  disproof.  If  it  be  said 
that  no  one  could  have  been  aware  of  this  in  the  absence 
of  publication,  I  reply  that  I  think  it  may  be  perceived 
by  any  one  who  reads  attentively  his  chapter  on 
Pangenesis.       Moreover,    early    in    the   seventies   his 


Preface. 


IX 


n  the  second 
cismann.  It 
hat  he  never 
cars  ago,  and 
I  independent 

that  to  him 
I  the  first  to 

so  to  arouse 
•  it.  But  to 
)pounded   by 

of  acquaint- 
)ught  in  this 
ng  conversa- 
er,  and  under 
are  the  only 

been  under- 
d  more  than 
on ;  but,  as 
er  published. 

for  the  pur- 
s  now  called 
5ent  to  Dar- 
lative  to  the 
ngenesis — an 
siious  to   ex- 

If  it  be  said 
1  the  absence 

be  perceived 

chapter  on 
seventies   his 


cousin,  Mr.  Francis  Galton,  published  a  "  Theory  of 
Heredity,"  which,  as  we  shall  see  in  the  course  of 
the  following  pages,  presented  as  distinctly  as  could 
possibly  be  presented  the  question  of  the  transmission 
of  acquired  characters,  and  answered  it  in  almost 
exactly  the  same  manner  as  Weismann  did  about  ten 
years  later.  Lastly,  as  Weismann  has  himself  been 
careful  to  point  out,  he  was  likewise  anticipated  in  thi.s 
matter  by  Jiiger  (1S78),  and  Nussbaum  and  Raubcr 
(1880). 

For  these  reasons,  then,  I  exclude  this  question 
from  the  following  examination  of  what  I  think  we 
ought  to  understand  as  distinctively  '•  Wcismannism." 


G.  J.  R. 


Christ  Church,  Oxford, 
July,  '89.'^ 


n 


<-  C  t  I  c 


C: 


■HP 


■■■■1 


1 


1 


AN 


]  EXAMINATION  OF  WEISMANNISM. 


CHAPTER   I. 

Statkment  of  VVfcismann's  System 
UP  TO  THE  Year  i8(S6i. 

Seeing    that    Professor    Weismann's    theory    of 
heredity,  besides  being  somewhat  elaborate  in  itself,  is 
presented  in  a  series  of  disconnected  essays,  originally 
published  at  different  times,  it  is  a  matter  of  no  small 
difficulty    to   gather  from    the  present    collection  of 
them   a  complete  view  of  the   system    as   a   whole. 
Therefore   I  propose    to  give  a  brief   sketch  of   his 
several    cognate    theories,    arranged     in     a    manner 
calculated  to  show  their  logical  connexion  one  with 
another.     And,  in  order  also  to  show  the  relation  in 
which  his  resulting  theory  of  hcredi.y  stands  to  what 
has  hitherto  been  the  more  usual  way  of  regarding 
the  facts,  I  will  begin  by  furnishing  a  similarly  con- 
densed   accoii.     of  Mr.   Darwin's    theory   upon    the 
subject.     It  will  be  observed  that  these  two  theories 
constitute  the  logical  extremes  of  explanatory  thought  • 
and  therefore  it  may  be  said,  in  a  general  way,  that 

'  Considerable  portions  of  this  chapter  have  already  appeared  as  an 
article  .„  th.  Confe„,j,orary  /Review  for  May.  iSyo.  Mv  tlanks  are  due 
to  the  editor  for  kindly  allowing  n>e  to  reproduce  them  L 


TT 


^ 


,  t 


I  <:  *    f 


a        /In  Exauiination  of  IVcisiiianmsin. 

all  other  modern  theories  of  heredity — such  as  those  of 
Spencer,  H.ickel,  Elsberg,  Galton,  Niigeli,  His,  Brooks, 
Hertvvig.  and  De  Vries — occupy  positions  more  or  less 
intermediate  between  these  two  extremes.  Therefore, 
also,  we  need  not  wait  to  consider  these  intermediate 
theories  ^ 

When  closely  analyzed,  Mr.  Darwin's  theory — or 
the  "  provisional  hypothesis  of  Pangenesis  " — will 
be  found  to  embody  aUogethcr  seven  assumptions, 
namely  : — 

1.  That  all  the  component  cells  of  a  multicellular 
organism  throw  off  inconceivably  minute  germs,  or 
"  gemmules,"  which  are  then  dispersed  throughout  the 
whole  system. 

2.  That  these  gemmules,  when  so  dispersed  and 
supplied  with  proper  nutriment,  multiply  by  self- 
dnnsipn,  and,  under  suitable  conditions,  are  capable  of 
developing  into  physiological  cells  like  those  from 
which  they  were  originally  and  severally  derived. 

3.  That,  while  still  in  this  gemmular  condition, 
these  cell-seeds  have  for  one  another  a  mutual  affinity, 
which  leads  to  their  being  collected  from  all  parts  of 
the  system  by  the  reproductive  glands  of  the  organ- 
isHT;  and  that,  when  so  collected,  they  go  to  con- 
stitute the  essential  material  of  the  sexual  elemenfs — 

*  Til  as  far  ns  these  sundry  tbcorics  of  heredity  are  not  more  or  less 
intermediate  between  those  of  I  arwin  and  Weismann,  the  differences 
have  reference  cither  to  points  of  comparative  detail,  or  else  to  the 
introduction  of  ideas  derived  from  chemistry  and  physics — whereby  it 
is  sought  to  show  that  the  jirinciples  of  chemical  combination  and.  of 
rhythmic  vibration  may  have  a  more  or  less  considerable  share,  in  the 
matter.  For  my  own  j)art  I  do  not  see  that  the  introduction  of  such 
ideas  has  been  of  any  avail  in  lielpinp — even  hypothetically — to  explain 
the  phenomena  of  heredity;  and  therefore  I  do  not  deem  it  worth  our 
.vhilc  to  consider  them. 


m 


msm. 


Statement  of  Weismanns  System  (1886).     3 


:h  as  those  of 
His,  Brooks, 
more  or  less 
.  Therefore, 
intermediate 

>  theory — or 
;nesis  " — will 
assumptions, 

multicellular 
te  germs,  or 
roughout  the 

ispersed  and 
ply  by  self- 
ire  capable  of 
those  from 
derived, 
ir  condition, 
utual  affinity, 
all  parts  of 
the  organ - 
go  to  con- 
elemenfs — 

lot  more  or  less 
the  differences 
,  or  else  to  the 
sics — whereby  it 
ibination  and.  of 
ble  share,  in  the 
duction  of  such 
ally — to  explain 
em  it  worth  our 


■1 
•I 


"! 


ova  and  spermatozoa  being  thus  aggregated  packets 
of  gemmules,  which  have  emanated  from  all  the  cells 
of  all  the  tissues  of  the  organisrn. 

4.  That  the  development  of  a  new  organism,  out  of 
the  fusion  of  two  such  packets  of  gemmules,  is  due  to 
a  summation  of  all  the  developments  of  some  of  the 
gemmules  which  these  two  packets  contain. 

5.  That  ajarge  proportional  number  of  the  gem- 
mules in  each  packet,  however,  fail  to  deyclop,  and 
are  then  transmitted  in  a  dormant  state  to  future 
generations,  in  any  of  which  they  may  be  developed 
subsequently — thus  giving  rise  to  the  phenomena  of 
reversion  or  atavism. 

6.  That  in  all  cases  the  development  of  gemmules 
into  the  form  of  their  parent  cells  depends  on  their 
suitable  union  with  other  partially  developed  gem- 
mules, which  precede  them  in  the  regular  course  of 
growth. 

7.  That  gemmules  are  thrown  off  by  all  physio- 
logical cells,  not  only  during  the  adult  state  of  the 
organism,  but  during  all  stages  of  its  development. 
Or,  in  other  words,  that  the  production  of  these  cell- 
seeds  depends  upon  the  adult  condition  of  parent  cells : 
not  upon  that  of  the  multicellular  organism  as  a 
whole. 

At  first  sight  it  may  well  appear  that  we  have 
here  a  very  formidable  array  of  assumptions.  But 
Darwin  ably  argues  in  favour  of  each  of  them  by 
pointing  to  well-known  analogies,  drawn  from  the 
vital  processes  of  living  cells  both  in  the  protozoa 
and  metazoa.  For  example,  it  is  already  a  well- 
recognized  doctrine  of  physiology  that  each  cell  of 
a  metazoon,   or   multicellular   organism,   thowgh   to 

B  2 


f1 


rf^Tf- 


''1 


,  ) 


4        An  Examination  of  Weis?nannism. 

a  lar^Tc  extent  dependent  on  others,  is  likewise  to 
a  certain  extent  independent  or  autonomous,  and  has 
the  power  of  multiplying  by  self-division.  Therefore, 
as  it  is  certain  that  the  sexual  elements  (and  also  buds 
of  all  descriptions)  include  formative  material  of  some 
kind,  the  first  assumption  —  or  that  which  supposes  such 
formative  matter  to  be  particulate — is  certainly  not 
a  gratuitous  assumption. 

Again,  the  second  assumption — viz.,  that  this  par- 
ticulate and  formative  material  is  dispersed  throughout 
all  the  tissues  of  the  organism — is  sustained  by  the  fact 
that,  both  in  certain  plants  and  in  certain  invertebratcd 
animals,  a  severed  portion  of  the  organism  will  develop 
into  an  entire  organism  similar  to  that  from  which  it 
was  derived,  as,  for  example,  is  the  case  with  a  leaf  of 
Begonia,  and  with  portions  cut  from  certain  inver- 
tebratcd arimals,  such  as  sea-anemones,  jelly-fish,  &c. 
This  well-known  fact  in  itself  seems  enough  to  prove 
that  the  formative  material  in  question  must  certainly 
admit,  at  all  events  in  many  cases,  of  being  distributed 
throughout  all  the  tissues  of  living  organisms. 

The  third  assumption — or  that  which  supposes 
the  formative  material  to  be  especially  aggregated  in 
the  sexual  elements — is  not  so  much  an  assumption 
as  a  statement  of  obvious  fact  ;  while  the  fourth,  fifth, 
sixth,  .nd  seventh  assumptions  all  folloAv  deductively 
from  their  predecessors.  In  other  words,  if  the  first 
and  second  assumptions  be  granted,  and  if  the  theory 
is  to  comprise  all  the  facts  of  heredity,  then  the 
remaining  five  assumptions  are  bound  to  follow. 

To  the  probable  objection  that  the  supposed  gem- 
mules  must  be  of  a  size  impossibly  minute — seeing 
that  thousands  of  millions  of  them    would  have  to 


Statevjcnt  of  Weismanns  System  (1886).     5 


\  by  the  fact 
nvertebratcd 
will  develop 
rom  which  it 
vith  a  leaf  of 
ertain  inver- 
iclly-fish,  &c. 
Ligh  to  prove 
lUst  certainly 
distributed 
sms. 

;h    supposes 

ggregated  in 

assumption 

fourth,  fifth, 

deductively 

;,  if  the  first 

f  the  theory 

y,  then  the 

ollow. 

)poscd  gem- 
mte — seeing 
uld  have  to 


be  packed  into  a  single  ovum  or  spermatozoon — 
Darwin  opposes  a  calculation  that  a  cube_of_glass  or 
water,  having  only  one  ten-thousandth  of  an  incb_tQ 
a  side,  contaTiis"  somewhere  between  sixteen  and  a 
hundred" and  thirty-one  billions  of  molccuJcs.  Again, 
as  touching  the  supposed  power  of  multiplication  on 
the  part  of  his  gemmulcs,  he  alludes  to  the  fact 
that  infectious  material  of  all  kinds  exhibits  a  ratio 
of  increase  quite  as  great  as  any  that  his  theory 
requires  to  attribute  to  gemrnulcs.  Furthermore,  with 
respect  to  the  elective  affinity  of  gcmmules,  he 
remarks  that  "  in  all  ordinary  cases  of  sexual  repro- 
duction, the  male  and  female  elements  certainly  have 
an  elective  affinity  for  each  other " :  of  the  ten 
thousand  species  of  Coviposifac,  for  example,  "  there 
can  be  no  doubt  that  if  the  pollen  of  all  these 
species  could  be  simultaneously  placed  on  the  stigma 
ofany  one  species,  this  one  would  elect,  with  unerring 
certainty,  its  own  pollen." 
"^uch,  in  brief  outline,  is  Mr.  Darwin's  theory  of 
Pangenesis. 

Professor  Weismann's  theory  of  Germ-plasm  is 
fundamentally  based  upon  the  great  distinction, 
in  respect  of  their  transmissibility,  between  char- 
acters that  are  congenital  and  characters  that  are 
acquired.  By  a  congenital  character  is  meant  any 
individual  peculiarity," whether  structural  or  mental, 
with  wHicK' the  individual  is  born.  By  an  acquired 
cHai-acter  is  meant  any  peculiarity  which  the  individual 
may  subsequently  develop  in  consequence  of  its  own 
individual  experience.  For  example,  a  man  may  be 
born  with  sonie  malformation  of  one  of  his  fingers  ;  or 
he  may  subsequently  acquire  such  a  malformation  as 


-rwrr 


f  -1 


■Hi: 


6        An  Examination  of  Weismannism. 

the  result  of  accident  or  disease.  Now,  in  the  former 
case — i.e.,  in  that  where  the  malformation  is  con- 
genital—it is  extremely  probable  that  the  peculiarity 
will  be  transmitted  to  his  children  ;  while  in  the  latter 
case — i.e.,  where  the  malformation  is  subsequently 
acquired  — it  is  virtually  certain  that  it  will  not  be 
transmitted  to  his  children.  And  this  great  difiference 
between  the  transmissibility  of  characters  that  are 
congenital  and  characters  that  are  acquired  extends 
universally  as  a  general  Ir.w  throughout  the  vegetable 
as  well  as  the  animal  kingdom,  and  in  the  province  of 
mental  as  in  that  of  bodily  organization.  Of  course 
this  gengrgl  hiw  has  always  been  well  known,  and 
more  or  less  fully  recognized  by  all  modern  physi- 
ologists and  medical  men-  I^ut  before  the  subject 
was  taken  up  by  Professor  Weismann,  it  was  generally 
supposed  that  the  difference  in  question  was  one  of 
degree,  not  one  of  kind.  In  other  words,  it  was 
assumed  that  acquired  characters,  although  not  so 
fully — and  therefore  not  so  certainly — inherited  as 
congenital  characters,  nevertheless  were  inherited  in 
some  lesser  degree  ;  so  that  if  the  same  character 
continued  to  be  developed  successively  in  a  number 
of  sequent  generations,  what  was  at  first  only  a  slight 
tendency  to  be  inherited  would  become  by  summation 
a  more  and  more  pronounced  tendency,  till  eventually 
the  acquired  character  might  be  as  strongly  inherited 
as  any  other  character  which  was  ab  initio  congeixital. 
Now  it  is  the  validity  of  this  assumption  that  is 
challenged  by  Professor  Weismann.  He  says  there  is 
no  evidence  of  any  acquired  characters  being  in  any 
degree  inherited  ;  and,  therefore,  that  in  this  important 
respect  they  may  be  held  to  differ  from  congenital 


Statement  of  Weismanns  System  (1886).     7 

characters  in  kind.  On  the  supposition  that  they  do 
thus  difi'er  in  kind,  he  furnishes  a  very  attractive 
theory  of  heredity,  which  serves  at  once  to  explain 
the  difference,  and  to  represent  it  as  a  matter  of 
physiolofjical  impossibility  that  any  acquired  char- 
acter can,  under  any  circumstances  whatsoever,  be 
transmitted  to  progeny. 

But,  in  order  fully  to  comprehend  this  theory,  it  is 
desirable  first  of  all  to  explain  Professor  VV'eismann's 
views  upon  certain  other  topics  which  are  intimately 
connected  with — and,  indeed,  logically  sequent  upon — 
the  use  to  which  he  puts  the  distinction  just  men- 
tioned. 

Starting  from  the  fact  that  unicellular  organisms    , 
multiply  by  fission  and  gemmation,  he  argues  that,^,^^/^».j/^ 
aboriginally  and  potentially,  life  is  immortal.      For  0 

when  a  protozoon  divides  itself  into  two  more  or  less 
equal  parts  by  fission,  and  each  of  the  two  halves 
thereupon  grows  into  another  protozoon,  it  does  not 
appear  that  there  has  been  any  death  on  the  part  of 
the  living  material  involved  ;  and  inasmuch  as  this 
process  of  fission  goes  on  continuously  from  generation 
to  generation,  there  is  seemingly  never  any  death 
on  the  part  of  such  protoplasmic  material,  although 
there  is  a  continuous  addition  to  it  as  the  numbers 
of  individuals  increase.  Similarly,  in  the  case  of 
gemmation,  when  a  protozoon  parts  with  a  small 
portion  of  its  living  material  in  the  form  of  a  bud, 
this  portion  does  not  die,  but  devclo[)s  into  a  new 
individual ;  and,  therefore,  the  process  is  exactly 
analogous  to  that  of  fission,  save  that  a  small 
instead  of  a  large  part  of  the  parent  substance  is 
involved.      Now,    if    life    be    thus    immortal    in   the 


■fm* 


i  II' 


i      i 


8        y/;/  Examination  of  irdsnianuism. 

case  of  unicellular  organisms,  why  should  it  have 
ceased  to  be  so  in  the  case  of  multicellular?  Weis- 
mann's  answer  is,  that  all  the  multicellular  orj^anisnis 
propagate  themselves,  not  exclusively  by  fission  or 
gemmation,  but  by  sexual  fertilization,  where  the 
condition  to  a  new  organism  arising  is  that  minute 
and  specialized  portions  of  two  parent  organisius 
should  fuse  together.  Now,  it  is  evident  that  with 
this  change  in  the  method  of  propagation,  serious 
disadvantage  would  accrue  to  any  species  if  its  sexual 
individuals  were  to  continue  to  be  immortal ;  for  in 
that  case  every  species  which  multiplies  by  sexual 
methods  would  in  time  become  composed  of  indi- 
viduals broken  down  and  decrepit  through  the  results 
of  accident  and  disease — always  operating  and  ever 
accumulating  throughout  the  course  of  their  immortal 
lives.  Consequently,  as  soon  as  i^cxual  methods  of 
propagation  superseded  the  more  primitive  a-sexual 
methods,  it  became  desirable  in  the  interests  of  the 
sexually-propagating  species  that  their  constituent 
individuals  should  cease  to  be  immortal,  so  that  the 
species  should  always  be  recuperated  by  fresh,  young, 
and  well-formed  representatives.  Consequently,  also, 
natural  selection  would  speedily  see  to  it  that  all 
sexually-propagating  species  should  become  deprived 
of  the  aboriginal  endowment  of  immorality,  with  the 
result  that  death  is  now  universal  among  all  the 
individuals  of  such  species — that  is  to  say,  among 
all  the  metazoa  and  metaphyta.  Nevertheless,  it  is 
to  be  remembered  that  this  destiny  extends  only  to 
the  parts  of  the  individual  other  than  the  contents 
of  those  specialized  cells  which  constitute  the  repro- 
ductive elements.      For   although  in  each  individual 


Ill  sin. 


Statement  of  IWisnuinns  System  (1886).     9 


lid    it   liave 
lar?     Wcis- 
r  organisms 
y  fission  or 
where    the 
tliat   minute 
t    organisms 
It  that   with 
Lion,  serious 
if  its  sexual 
irtal ;   for  in 
s  by  sexual 
scd  of  indi- 
h  the  results 
ng  and  ever 
eir  immortal 
methods  of 
ive  a-scxual 
rests  of  the 
constituent 
so  that  the 
resh,  younf:^, 
uently,  also, 
it    that   all 
me  deprived 
ty,  with  the 
long  all    the 
say,  among 
thcless,  it  is 
nds  only  to 
he   contents 
e  the  repro- 
h  individual 


metazoon  or  metaphyton  an  innumerable  number  of 
these  specialized  cells  arc  destined  to  perish  during 
the  life,  or  with  the  death,  of  the  organism  to  which 
they  belong,  this  is  only  due  to  the  accident,  so  to 
speak,  of  their  contents  not  h.iving  met  with  their 
complements  in  the  opposite  sex  :  it  (^K^^-f,  not  belong 
to  their  essential  nature  that  they  shoultl  pirish,  seeing 
that  those  which  do  happen  to  meet  with  their  com- 
plements in  the  opposite  sex  help  to  form  a  new  living 
individual,  and  so  on  through  successive  generations 
ad  infinitum.  Therefore  the  reproductive  elements 
of  the  meta/.oa  and  nutaphyta  are  in  this  respect 
precisely  analogous  to  the  protozqa  :  potentially,  or  in 
their  own  nature,  they  arc  immortal ;  andMJke^thc 
protozoa,  if  they  die.  their  death  is  an  accident  duc_to 
unfavourable  circumstar.  "es.  But  the  case  Js  cpjite 
different  with  a^'  the  other  parts  of  a  multicellular 
organism.  Mere,  no  matter  how  favourable  the  cir- 
cumstances may  be,  every  cell  contains  within  itself, 
or  in  its  very  nature,  the  eventual  doom  of  death. 
Thus,  of  the  mctazoa  and  metaphyta  it  is  the 
"  germ-plasms "  alone  that  retain  their  primitive 
endowment  of  everlasting  life,  passed  on  continuously 
through  generation  after  generation  of  successively 
perishing  organisms. 

So  far,  it  is  contended,  we  are  dealing  with  matters 
of  fact.  It  must  be  taker,  as  true  that  the  protoplasm 
of  the  unicellular  organisms,  and  the  germ-plasm  of  the 
multicellular  organisms,  has  been  continuous  through 
the  time  since  life  first  appeared  upon  this  earth  ;  and 
although  large  quantities  of  each  are  perpetually  dying 
through  being  exposed  to  conditions  unfa\ourable  to 
life,  this,  as  Weismann  presents  the  matter,  is  quite 


7T 


"ir^ 


'    ■  •  ■  ^ 


lo      An  Examination  of  Weismannism. 

a  dififerent  case  from  that  of  all  the  othe/  constituent 
parts  of  multicellular  organisms,  which  contain  within 
themselves  the  doom  of  death.  Furthermore,  it  appears 
extremely  probable  that  this  doom  of  death  has  been 
brought  about  by  natural  selection  for  the  reasons 
assigned  by  Weismann— namely,  because  it  is  for  the 
benefit  of  all  species  which  perpetuate  themselves  by 
sexual  methods,  that  their  constituent  individuals 
should  not  live  longer  than  is  necessary  for  the  sake 
of  orginating  the  next  generation,  and  fairly  starting 
it  in  its  own  struggle  for  existence.  For  Weismann 
has  shown,  by  a  somewhat  laborious  though  still 
largely  imperfect  research,  that  there  is  throughout 
all  the  metazoa  a  general  correlation  between  the 
natural  lifetime  of  individuals  composing  any  given 
species  and  the  age  at  which  they  reach  maturity, 
or  first  become  capable  of  procreation.  This  general 
correlation,  however,  is  somewhat  modified  by  the 
time  during  which  progeny  are  dependent  upon  their 
parents  for  support  and  protection.  Nevertheless, 
it  is  evident  that  this  fact  tends  rather  to  confirm 
the  view  that  expcctvation  of  life  on  the  part  of 
individuals  has  in  all  cases  been  determined  with 
strict  reference  to  the  requirements  of  propagation, 
if  under  propagation  we  include  the  rearing  as  well 
as  the  production  of  offspring.  I  may  observe  in 
passing  that  I  do  not  think  this  general  law  can 
be  found  to  apply  to  plants  in  nearly  so  close 
a  manner  as  Weismann  has  shown  it  to  apply  to 
animals ;  but,  leaving  this  consideration  aside,  I  think 
that  Weismann  has  made  out  a  good  case  in  favour 
of  such  a  general  law  with  regard  to  animals*. 

*  Sue  Appendix. 


j^i 


^r/' 


Statement  of  Wcisinanns  System  (1886).    11 


constituent 
itain  within 
e,  it  appears 
th  has  been 
the  reasons 
it  is  for  the 
jmselves  by 
individuals 
or  the  sake 
iriy  starting 
*  Weismann 
though  still 
throughout 
jetvveen  the 
I  any  given 
:h  maturity, 
rhis  general 
fied  by  the 
t  upon  their 
evertheless, 
to  confirm 
he    part   of 
mined  with 
propagation, 
ing  as  well 
observe    in 
al   law  can 
y   so    close 
o  apply  to 
5ide,  I  think 
e  in  favour 
mals  ^. 


We  have  come,  th^n,  to  these  results.  Proto- 
plasm v;as  originally  immortal,  barring  accidents ; 
and  it  still  continues  to  be  immortal  in  the  case  of 
unicellular  organisms  which  propagate  a-sexually. 
But  in  the  case  of  all  multicellular  organisms,  which 
propagate  sexually,  natural  selection  has  reduced 
the  term  of  life  within  the  smallest  limits  that  in 
each  given  case  are  compatible  with  the  performance 
of  the  sexual  act  and  the  subsequent  rearing  of  ])ro- 
geny — reserving,  however,  the  original  endownsent 
of  immortality  for  the  germinal  elements,  whereby 
a  contimmm  of  life  has  been  secured  from  the  earliest 
appearance  of  life  until  the  present  day. 

Now,  in  view  of  these  results  the  question  arises, — 
Why  should  the  sexual  methods  of  propagation  have 
become  so  general,  if  their  effect  has  been  that  of 
determining  the  necessary  death  of  all  individuals 
presenting  them  ?  Why,  in  the  course  of  organic 
evolution,  should  these  newer  methods  have  been 
imposed  on  all  the  higher  organisms,  when  the  conse- 
quence is  that  all  these  higher  organisms  must  pay 
for  the  innovation  with  tlieir  lives?  Weismann's 
answer  to  this  question  is  as  inteiesting  and  ingenious 
as  all  that  has  gone  before.  Seeing  that  sexual  pro- 
pagation is  so  general  as  to  be  practically  universal 
among  multicellular  organisms,  it  is  obvious  that  in 
some  way  or  another  it  must  have  had  a  most  important 
part  to  play  in  the  general  scheme  of  organic  evolution. 
What,  then,  is  the  part  that  it  does  play?  What  is 
its  raison  d'etre  ?  Briefly,  according  to  Weismann,  its 
function  is  j^iat  of  furmshiiig  congenital  variations  to 
the  jever;^atchful  agency  of  natural  selection,^  in  order 
that  natural  selection  may  always  prcseive  the  most 


J 


^r 


>  <  ill 
i  ill 


12      An  Examination  of  Weismannism, 

favourable,  and  pass  them  on  to  the  next  generation 
by  heredity.  That  sexual  propagation  is  well  calcu- 
lated to  furnish  congenital  variations  may  easily  be 
rendered  apparent.  We  have  only  to  remember  that 
at  each  union  there  is  a  mixture  of  two  sets  of 
germinal  elements  ;  that  each  of  these  was  in  turn 
the  product  of  two  other  sets  in  the  preceding 
generation,  and  so  backwards  ad  infinitum  in  an 
ever  doubling  ratio.  Remembering  this,  it  follows 
that  the  germinal  elements  of  no  one  member,  of 
a  s£ecies  can  ever  be  the  same  as  those  of  any.  other 
member  born  of  different  parents ;  on  the  contrary, 
while  both  are  enormously  complex  products,  each 
has  had  a  different  ancestral  history,  such  that 
while  one  presents  the  congenital  admixtures  of 
thousands  of  individuals  in  one  line  of  descent,  the 
other  presents  similar  admixtures  of  thousands  of 
other  individuals  in  a  different  line  of  descent.  Con- 
sequently, when  in  any  sexual  union  two  of  these 
enormously  complex  germinal  elements  fuse  together, 
and  constitute  a  new  individual  out  of  their  joint 
endowments,  it  is  perfectly  certain  that  that  individual 
cannot  be  exactly  like  any  other  individual  of  the 
same  species  which  has  been  born  of  different  parents. 
The  chances  must  be  infinity  to  one  aga'nst  any  single 
mass  of  germ-plasm  being  exactly  like  any  other  mass 
of  germ-plasm  ;  while  any  amount  of  latitude  as  to 
difference  is  allowed,  up  to  the  point  at  which  the 
difference  becomes  too  pronounced  to  satisfy  the 
conditions  of  fertilization — in  which  case,  of  course, 
no  new  individual  is  born.  Hence,  theoretically,  we 
have  here  a  sufficient  cause  for  all  individual  variations 
of  a  congenital  kind  that  can  possibly  occur  within 


msm. 


Slat' men t  of  Weistnaitns  Sys/e f u  (iSS6).     13 


t  generation 

(  well  caicu- 

y  easily  be 

nember  that 

two   sets   of 

was  in  turn 

e   precedinij 

i/?itn   in   an 

3,  it  follows 

member,  of 

)f  any.  other 

le   contrary, 

iducts,   each 

such    that 

mixtures    of 

descent,  the 

liousands   of 

cent.     Con- 

vo   of  these 

ise  together, 

their  joint 

it  individual 

dual   of  the 

ent  parents. 

t  any  single 

other  mass 

titude  as  to 

which   the 

satisfy   the 

,  of  course, 

etically,  we 

il  variations 

>ccur  within 


the  limits  of  fertility,  and,  therefore,  that  can  ever 
become  actual  in  living  organisms.  In  point  of  fact, 
Wcismann  believes — or,  at  any  rate,  provisionally 
maintains — that  this  is  the  sole  .and  only  causQ  of 
variations  that  are  congenital,  and  therefore  (according 
to  his  views)  transmissible  by  heredity.  Now,  whether 
or  not  he  is  right  as  regards  these  latter  points,  I 
think  there  can  be  n^3_^uestion  that  sexual  propagation 
is,  at  all  events,  one  of  the  rnain  causes  of  congenital 
variation  ;  and  seeing  of  what  enormous  importance 
congenital  variation  m.ust  always  nave  been  in 
supplying  material  for  the  operation  of  natural  se- 
lection, we  appear  to  have  found  a  most  satisfactory 
answer  to  our  question, — Why  has  sexual  propagation 
become  so  universal  among  all  the  higher  plants  and 
animals?  IthcUL-bxiCQnie  so  because  it  is  thus  shown  •  ^^^ 
to  have  been  the  condition  to  producing  congenital/^  /  ///> 
variations,  which  in  turn  constitute  one  of  the  primary  ^  1  ^^ 
conditions  to  the  working  of  natural  selection. 

Having  got  thus  far,  I  should  like  to  make  two  or 
three  subsidiary  remarks.  In  the  first  place,  it  ought 
to  be  observed  that  this  theory  touching  the  causes  of 
congenital  variations  was  not  originally  propounded 
bj^Professor  Weismann,  but  occurs  in  the  writings  of 
several  previous  authors,  and  is  expressly  alluded  to 
by  Darwin  ^  Nevertheless,  it  occupies  so  prominent 
a  place  in  Weismann's  system  of  theories,  and  has  by 
him  been  wrought  up  so  much  more  elaborately  than 
by  any  of  his  predecessors,  that  we  are  entitled  to 
regard  it  as,  par  excellence,  the  Weismannian  theory  of 
variation.  In^the  next  place,  it  ought  to  be  observed 
that  Weismann  is  careful  t-  guard  against^tlic 
•  E.g.,  Variation,  &c.,  vol.  i.  pp.  197,  398;  vol.  ii.  pp.  237,  252. 


t4U^  tv^      Cf 


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•  •   • 

ft   •   * 

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III 


14      An  Examination  of  Weismannism. 

seductive  fallacy  of  attributing  the  origin  of  sexual 
propagation  to  the  agency  of  natural  selection.  Great 
as  the  benefit  of  this  newer  mode  of  propagation  must 
have  been  to  the  species  presenting  it,  the  benefit 
cannot  have  been  conferred  by  natural  selection, 
seeing  that  the  benefit  arose  from  the  fact  of  the 
new  method  furnishing  material  to  the  operation 
of  natural  selection,  and  therefore  constituting  the 
condition  to  the  agency  of  natural  selection  having 
been  called  into  exiGiance  at  all.  Or,  in  other 
words,  we  cannot  attribute  to  natural  selection 
the  origin  of  sexual  reproduction  without  involv- 
ing ourselves  in  the  absurdity  of  supposing  natural 
selection  to  have  originated  the  conditions  of  its 
own    activity '.      What   the   causes    may    have   been 

'  Since  this  chapter  was  written  and  sent  as  a  contribution  to  the 
Contemporary  Revic^v,  Professor  Weismann  has  published  in  Nature 
(Feb.  6,  1890)  an  elaborate  answer  to  a  criticism  of  his  theory  by 
Professor  Vines  (Oct.  24,  1889).  In  the  course  of  this  answer  Professor 
NVeismann  saysthat  he  </<mj  attribute  the  origin  of  sexual  reproduction 
to  natural  selection.  This  directly  contradicts  what  he  says  in  his 
Essays ;  aiu!,  for  the  reasons  given  in  the  text,  appears  to  me  an  illogical 
departure  from  his  previously  logical  attitude.  I  herewith  appenil 
quotations,  in  order  to  reveal  the  contradiction. 

"  But  when  I  maintain  that  the  meaning  of  sexual  reproduction  is  to 
render  possible  tiie  transformation  of  the  higher  organisms  by  means  of 
natural  selection,  such  a  statement  is  not  equivalent  to  the  assertion  that 
sexual  reproduction  originally  came  into  existence  in  order  to  achieve 
this  end.  The  effects  which  are  now  protiuced  by  sexual  reproduction 
did  not  constitute  the  causes  which  led  to  its  first  appearance.  Sexual 
reproduction  came  into  existence  before  it  could  lead  to  hereditary 
individual  variability  [i.e.,  to  the  possibility  of  natural  selection].  Its 
first  appearance  must,  therefore,  have  had  some  other  cause  [than 
natural  selection]  ;  but  the  nature  of  this  cause  can  hardly  be  determined 
with  any  degree  of  certainty  or  precision  from  the  facts  with  which  we 
are  at  present  acciuainted." — Essay  on  the  Signijicance  of  Sexual  Re- 
production in  the  Theory  of  Natural  Selection.  English  Translation, 
pp.  2S1    282. 

"  I  am  still  of  opinion  that  the  origin  of  sexual  reproduction  depends 


i 


I 

■9 


ism. 


Statement  of  Weismami  s  System  (1886).     15 


I  of  sexual 
ion.     Great 
gation  must 
the   benefit 
1    selection, 
fact  of  the 
I    operation 
tituting   the 
:tion  having 
r,    in    other 
al    selection 
lout   involv- 
sing  natural 
tions   of   its 
have   been 

itribution  to  the 
ihecl  in  Nature 
f  his  theory  by 
insvver  Professor 
xsX  reproduction 
he  says  in  his 
me  an  illo{;ical 
lerewith  append 

production  is  to 
sms  by  means  of 
le  assertion  that 
jrder  to  achieve 
ual  reproduction 

arance.  Sexual 
,d  to   hereditary 

selection].  Its 
her  cause  [than 
ly  be  determined 

s  with  which  we 
<:e  of  Sexual  Ke- 

isli  Translation, 

duction  depends 


which  originally  led  to  sexual  reproduction  is  at 
present  a  matter  that  awaits  suggestion  by  way  of 
hypothesis;  and,  therefore,  it  now  only  remains  to  add 
that  the  general  structure  of  Professor  Weismann's 
system  of  hypotheses  leads  to  this  curious  result  — 
namely,  that  the  otherwise  ubiquitous  and  (as  he 
supposes)  exclusive  dominion  of  natural  selection 
stops  short  at  the  protozoa,  over  which  it  cannot 
exercise  any  inHucnce  at  all.  For  if  natural  selection 
depends  for  its  activity  on  the  occurrence  of  congenital 
vanationSj  and  if  congenital  variations  depend  for 
their  occurrence  on  sexual  modes  of  reproduction,  it 
follows  that  no  organisms  which  propagate  by  any 
other  modes  can  present  congenital  variations,  or  thus 
become  subject  to  the  sway  of  natural  selection. 
And  inasmuch  as  Weismann  believes  that  such  is  the 
case  with  all  the  protozoa,  as  well  as  with  all 
parthenogenctic  organisms  he  does  not  hesitate  to 
accept  the  necessary  conclusion  that  in  these  cases 
natural  selection  is  without  any  jurisdiction.  How, 
then,  does  he  account  for  individual  variations  in 
the  protozoa  ?  And,  still  more,  how  does  he  ac- 
count for  the  origin  of  their  innumerable  species  ? 
He  accounts  for  both  these  things  by  the  direct 
action  of  external  conditions  of  life.  In  other  words, 
so  far  as  the  unicellular  organisms  are  concerned, 
Weismann  IF  rigidly  and"  unconditionally  an  advocate 


on  the  advantage  which  it  afTdrds  to  the  operation  of  natural  selection. 
....  Sexual  rej)roduction  lias  arisen  by  and  for  natural  selcctinti  as  the 
sole  means  by  which  individual  variations  can  be  united  and  combined 
in  every  possible  proportion." — Nature,  vol.  xli.  p.  322. 

How  such  contradictory  statements  can  be  reconciled  I  do  not 
perceive;  but  they  furnish  a  ^ood  example  of  the  extreme  laxity  witii 
vvliich  the  term  '•  natural  selection  "  is  Uicd  by  ultra-Darwinians. 


^iiTir 


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1  • 


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m 


'Mi 


III!  I 


;.'ii 


1 6      An  Examination  of  Weismannism. 

of  the  theory  of  Lamarck — just  as  much  as  in  the  case 
of  all  the  multicellular  organisir,  i  he  is  ric^idly  and  un- 
conditionally an  opponent  of  that  theory.  Nevertheless, 
there  is  here  no  inconsistency :  on  the  contrary,  it  is 
consistency  with  the  logical  requirements  of  his  theory 
that  leads  to  this  sharp  partitioning  of  the  unicellular 
from  the  multicellular  organisms  with  respect  to  the 
causes  of  their  evolution.  For,  according  to  his  view, 
the  conditions  of  propagation  among  the  unicellular 
organisms  are  such  that  parent  and  offspring  are  one 
and  the  same  thing ;  "  the  child  is  a  part,  and  usually 
a  half,  of  its  parent."  Therefore,  if  the  parent  has 
been  in  any  way  modified  by  the  action  of  external 
conditions,  it  is  inevitable  that  the  child  should,  from 
the  moment  of  its  birth  (i.e.,  fissiparous  separation), 
be  siniilarly  modified  ;  and  if  the  modifying  influences 
continue  in  the  same  lines  for  a  sufficient  length  of 
time,  •  the  resulting  change  of  type  may  become 
sufficiently  pronounced  to  constitute  a  new  species, 
genus,  &c.  But  in  the  case  of  the  multicellular  or 
sexual  organisms,  the  child  is  not  thus  merely  a 
severed  moiety  of  its  parent ;  it  is  the  result  of  the 
fusion  of  two  highly  specialized  and  extremely  miinute 
particles  of  each  of  two  parents.  Therefore,  whatever 
may  be  thought  touching  the  validity  of  Weismann's 
deduction  that  in  no  case  can  any  modification  induced 
by  external  conditions  on  these  parents  be  trans- 
mitted to  their  progeny,  at  least  we  must  recognize 
the  validity  of  the  distinction  which  he  draws  between 
the  facility  with  which  such  transmission  must  take 
place  in  the  unicellular  organisms,  as  compared  with 
the  difficulty  — or,  as  he  believes,  the  impossibility — 
of  its  doing  so  in  the  multicellular. 


% 


'A  ■ 
I 


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lit 


nism. 

IS  in  the  case 
^idlyand  un- 
Nevertheless, 
:ontrary,  it  is 
of  his  theory 
le  unicellular 
espect  to  the 
T  to  his  view, 
le  unicellular 
3ring  are  one 
,  and  usually 
e  parent  has 
n  of  external 
should,  from 
5  separation), 
ing  influences 
ent  length  of 
may    become 

new  species, 
ilticellular  or 

us   merely  a 

result  of  the 
emely  minute 
ore,  whatever 
f  Weismann's 
;ation  induced 
its  be  trans- 
lust  recognize 

raws  between 
on  must  take 
om pared  with 
npossibility — 


Statement  of  IVeisuianti s  System  (1886).   17 

We  are  now  in  a  position  fully  to  understand  Pro- 
fessor Weismann's  theory  of  heredity  in  all  its  bearings. 
Briefly  stated,  it  is  as  follows.  The  whole  organiza- 
tion   of   any  jnulticelkilar    organisnL.js .CQOipiQ/^ed 

of  two  entirely  different  kinds  of  cclJs  — namely,  the 
germ-cells,  or  those  which  have  to  do  with  repro- 
duction, and  the  somatic-cells,  or  those  which  go  to 
constitute  all  the  other  parts  of  the  organism.  Now, 
the  somatic-cells,  in  their  aggregations  as  tissues  and 
organs,  may  be  modified  in  numberless  ways  by  the 
direct  action  of  the_enyirqnmcnt,  as  well  as  by  special 
habits  Formed  during  the  individual  hfetime  of  the 
organism.  15ut  although  the  modifications  thus  in- 
duced  may  be,  and  generally  are,  adaptive — such  as 
the  increased  musculanty;_caused  by  the  use  of  muscles, 
"  practice  making  perfect  "  where  neural  adjustments 
are  concerned,  and  so  on, — in  no  case  can  these  so- 
called  acquired,  or  "  somatogenetic,"  characters  exer- 
cise any  influence  upon  the  germ-cells,  such  that 
they  should  reappear  in  the  next  generation  as  con- 
genital, or  •'  blastogenetic."'  characters.  For,  according 
to  the  theory,  the  germ-cells  as  to  their  germinal 
contents  differ  in  kind  from  the  somatic-cells^_and 
have  no  other  connexion  or  dependence  upon  them 
than  that  of  deriving  from  them  their  food  and 
lodging.     So  much  for  the  somatic-cells. 

Turning  now  to  the  Gfcrm-cells,  these  are  the  re- 
ceptacles  of  what  Weismann  calls  the  germ-plasm  ; 
alid  tjiis  it  is  that  he  supposes  to  differ  in  kind 
from  all  the  other  constituent  elements  of  the 
organism.  For  the  germ-plasm  he  believes  to  have 
had  its  origin  in  the  unicellular  organisms,  and  to 
have  been  handed  down  from  them  in  one  continuous 

C 


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;M';i 


1 8      An  Examination  of  Wcisniannistn. 

stream  through  all  successive  generations  of  multi- 
cellular organisms.  Thus,  for  example,  suppose  that 
we  take  a  certain  quanttun  of  germ-plasm  as  this 
occurs  in  any  individual  organism  of  to-day.  A 
minute  portion  of  this  germ-plasm,  when  mixed 
with  a  similarly  minute  portion  from  another  in- 
dividual, goes  to  form  a  new  individual.  But,  in 
doing  so,  only  a  portion  of  this  minute  portion  is 
consumed  ;  tKe'  residue  is  stored  up  in  the  germinal 
cells  of  the  new  individual,  in  order  to  secure  that 
continuity  of  the  germ-plasm  which  Weismann 
assumes  as  the  necessary  basis  of  his  whole  theory. 
Furthermore,  he  assumes  that  this  overplus  portion  of 
germ-plasm,  which  is  .so  handed  over  to  the  custody 
of  the  new  individual,  is  there  capable  of  growth  or 
multiplication  at  the  expense  of  the  nutrient  materials 
which  are  supplied  to  it  by  the  new  soma  in  which 
it  finds  itself  located ;  while  in  thus  growing,  or 
multiplying,  it  faithfully  retains  its  highly  complex 
structure,  so  that  in  no  one  minute  particular  does 
any  part  of  a  many  thousand-fold  increase  differ,  as 
to  its  ancestral  characters,  from  that  inconceivably 
smaTT  overplus  which  was  first  of  all  entrusted  to  the 
emBryo  by  its  parents.  Therefore  one  might  re- 
present the  germ-plasm  by  the  metaphor  of  a  yeast- 
plant,  a  single  particle  of  which  may  be  put  into  a  vat 
of  nutrient  fluid  :  there  it  lives  and  grows  upon  the 
nutriment  supplied,  so  that  a  new  particle  may  next 
be  taken  to  impregnate  another  vat,  and  so  on  ad 
infiniUim.  Here  the  successive  vats  would  represent 
successive  generations  of  progeny;  but,  to  make  the 
metaphor  complete,  one  would  have  to  suppose  that 
in  each  case  the  yeast-cell  was  required  to  begin  by 


Statoncnt  of  lVci3})iadns  System  (icSSo).   19 

makincf  its  own  vat  of  nutrient  material,  and  that  it 
was  only  the  residual  portion  of  tlie  cell  whieh  was 
afterwards  able  to  grow  and  multiply.  But  althouijjh 
the  metaphor  is  thus  necessarily  a  clumsy  one,  it 
may  serve  to  emphasize  the  all-important  feature  of 
Weismann's  theory — namely,  the  ahiiost  absohite 
independence  of  the  germ-plasm.  For.  just  as  the 
properties  of  the  yeast-plant  would  be  in  no  way 
affected  by  anything  that  might  happen  to  the  vat, 
short  of  its  being  broken  up  or  having  its  malt 
impaired,  so,  according  to  Weismann,  the  properties 
of  the  germ- plasm  cannot  be  affected  by  anything 
that  may  happen  to  its  containing  soma,  short  of  the 
soma  being  destroyed  or  having  its  nutritive  functions 
disordered. 

Such  being  the  rc'ations  that  are  supposed  to 
obtain  between  the  soma  and  its  germ-plasm,  we  have 
next  to  observe  what  is  supposed  to  happen  when, 
in  the  course  of  evolution,  some  modification  of  the 
ancestral  form  of  the  soma  is  required  in  order  to 
adapt  it  to  some  change  on  the  part  of  its  environ- 
ment. In  other  words,  we  have  to  consider  Weis- 
mann's views  on  the  modus  operandi  of  adaptive 
development,  with  its  result  in  the  origination  of  new 
species. 

Seeing  that,  according  to  the  theory,  it  is  only  con- 
genital variations  which  can  be  inherited,  all  variations 
subsequently  acquired  by  the  intercourse  of  individuals 
with  their  environment,  however  beneficial  such 
variations  may  be  to  these  indivaduals,  are  ruled  out 
as  regards  the  species.  Not  falling  within  the 
province  of  heredity,  they  are  blocked  off  in  the  first 
generation,  and  therefore   present  no  significance  at 

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20      y^«  Examination  of  Wcismannism. 

all  in  the  process  of  organic  evolution.  No  matter 
how  many  generations  of  eagles,  for  instance,  may  have 
used  their  wings  for  purposes  of  flight  ;  and  no  matter 
how  great  an  increase  of  muscularity,  of  endurance,  and 
of  skill,  may  thus  have  been  secured  to  each  genera- 
tion of  eagles  as  the  result  of  individual  exercise  ; 
all  these  advantages  are  entirely  lost  to  progeny,  and 
young  eagles  have  ever  to  begin  their  lives  with  no 
more  benefit  bequeathed  by  the  activity  of  their 
ancestors  than  if  those  ancestors  had  all  been  barn- 
door fowls.  The  only  material  which  is  of  any  count 
as  regards  the  species,  or  with  reference  to  the  piOgess 
of  evolution,  are  fortuitous  variations  of  the  congenital 
k[nd.  Among  all  the  numberless  congenital  varia- 
tions, within  narrow  limits,  which  are  perpetually 
occurring  in  each  generation  of  eagles,  some  will  have 
reference  to  the  wings  ;  and  although  these  will  be 
fortuitous,  or  occurring  indiscriminately  in  all  direc- 
tions, a  few  of  them  will  now  and  then  be  in  the 
direction  of  increased  muscularity,  others  in  the 
direction  of  increased  endurance,  others  in  the  direc- 
tion of  increased  skill,  and  so  on.  Now  each  of  these 
fortuitous  variations,  which  happens  also  to  be  a 
beneficial  variation,  will  be  favoured  by  natural 
selection  ;  and,  because  it  likewise  happens  to  be  a 
congenital  variation,  will  be  perpetuated  by  heredity. 
InTthe  course  of  time,  other  congenital  variations  will 
happen  to  arise  in  the  same  directions ;  these  will  be 
added  by  natural  selection  to  the  advantage  already 
gained,  and  so  on,  till,  after  hundreds  and  thousands  of 
generations,  the  wings  of  eagles  have  become  evolved 
into  the  marvellous  structures  which  they  now  present. 
Such  being  the  theory  of  natural   selection  when 


State^ncnt  of  Wcismanns  System  (1886).   21 

stripped  of  all  remnants  of  so-called  Lamarckiaii 
principles,  we  have  next  to  consider  what  the  theory 
means  in  its  relation  to  germ-plasm.  For,  as  before 
explained,  congenital  variations  are  supposed  by 
VVeismann  to  be  due  to  new  combinations  taking 
place  in  the  germ-plasm  as  a  result  of  the  union  in 
every  act  of  fertilisation  of  two  complex  hereditary 
histories.  Well,  if  congenital  variations  are  thus 
nothing  more  than  variations  of  germ-plasm  "writ 
large  "  in  the  organism  which  is  developed  out  of  the 
plasm,  it  follows  that  natural  selection  is  really 
at  work  upon  these  variations  of  the  plasm.  For, 
although  it  is  proximately  at  work  on  the  congenital 
variations  of  organisms  after  birth,  it  is  ultimately, 
and  through  them,  at  work  upon  the  variations  of 
germ-plasm  out  of  which  the  organisms  arise.  In 
other  words,  natural  selection,  in  picking  out  of  each 
generation  those  individual  organisms  which  are  by 
their  congenital  characters  best  suited  to  their  sur- 
rounding conditions  of  life,  is  thereby  picking  out 
those  peculiar  combinations  or  variations  of  germ- 
plasm,  which,  when  expanded  into  a  resulting  organism, 
give  that  organism  the  best  chance  in  its  struggle  for 
existence.  And,  inasmuch  as  a  certain  overplus  of 
this  peculiar  combination  of  germ-plasm  is  entrusted  to 
that  organism  for  bequeathing  to  the  next  generation, 
this  to  the  next,  and  so  on,  it  follows  that  natural 
selection  is  all  the  while  conserving  that  originally 
peculiar  combination  of  germ-plasm,  until  it  happens 
to  meet  with  some  other  mass  of  germ-plasm  by  mixing 
with  which  it  may  still  further  improve  upon  its  original 
peculiarity,  when,  other  things  equal,  natural  selection 
will    seize    upon    this    improvement    to    perpetuate, 


•  r  '. 

•  •  I 

•  >  >   . 


I      ill 


I      ' 


i! 


iiii  ill 


1 1 


J'iil     :    i 


22      -//;/  Exanii nation  of  Wcismannism. 

as  in  the  prcviou.s  case.  So  that,  on  the  whoio,  we  may 
say  that  natural  selection  is  ever  waiting  and  watch- 
in<T  for  such  combinations  of  germ-plasm  as  will  give 
the  resulting  organisms  the  best  possible  chance  in 
their  struggle  for  existence ;  while,  at  the  same  time, 
it  is  remorselessly  destroying  all  those  combinations 
of  germ-plasm  which  are  handed  over  to  the  custody  of 
organisms  not  so  well  fitted  to  their  conditions  oflife. 

It  only  remains  to  add  that,  according  to  VVeis- 
mann's  theory  in  its  strictly  logical  form,  combinations 
of  germ-plasm  when  once  effected  are  so  stable  that 
they  would  never  alter  except  as  a  result  of  entering 
into  new  combinations.  In  other  words,  no  external 
influences  or  internal  processes  can  ever  change 
the  hereditary  nature  of  any  particular  mixture  of 
germ-plasm,  save  and  except  its  admixture  with 
some  other  germ-plasm,  which,  being  of  a  nature 
equally  stable,  goes  to  unite  with  the  fn-st  in  equal 
proportions  as  regards  hereditary  ch.  -acter.  So  that 
really  it  would  be  more  correct  to  say  i>  "-  any  given 
mass  of  germ-plasm  docs  not  change  eveii  "hen  it 
is  mixed  with  some  other  mass — any  more,  lor  in- 
stance, than  a  handful  of  sand  can  be  said  to  change 
when  it  is  mixed  with  a  handful  of  clay. 

Consequently,  wc  arrive  at  this  •.uriou'j  result. 
No  matter  how  many  generations  of  organisms  there 
nay  have  been,  and  therefore  no  ni:itl\jr  how  many 
combinations  of  germ-plasm  may  have  taken  place 
to  give  rise  to  an  existing  population,  each  existing 
unit  of  germ-plasni  must  have  remaincd^of  ihij—same 
essential  nature  or  constitution  as  _uhen_Jt  was_first 
started  in  its  immortal  career  millions  of  years^go. 
Or,  reverting  to  our  illustration  of  sand  and  clay,  the 


Statement  of  IW'isnianns  System  (1886).   2}^ 


particles  of  each  must  always  remain  the  same,  no 

matter   how    many   admixtures    they    may    undcr<To 

with  particles  of  other  materials,  such  as  chalk,  slate. 

&c.     Now,   inasmuch  as    it    is  an  essential  —  because 

a    lof^ically    necessary — part    of   VVcismann's   theory 

to  assume  such    absolute  stability  or  unchancjcable- 

ness  on  the  part  of  germ-plasm,  the  question  arises, 

and    has  to    be    met.  What  was  the  origin  of  those 

differences  of  character  in  the  different  rferm-plasms 
, .^.  .    -    p. r   — 

of  multicellular  organisms  wliich^  first  gave  rise,  and 
still  rnntinye  \i:)  give  rise^  to  congc^iital  variations 
by  their  mixture  one  with  another  ?  This  important 
question  Weismann  answers  by  supposing  that  these 
differences  originally  arose  out  of  the  dififcrcuces 
in  the  unicellular  organisms,  which  were  the  ancestors 
of  the  primitive  multicellular  organisms.  Now,  as 
before  stated,  different  forms  of  unicellular  organisms 
are  supposed  to  have  originated  as  so  many  results  of 
differences  in  the  direct  action  of  the  environment. 
Consequently,  according  to  the  theory,  all  congenital 
variations  which  now  occur  in  multicellular  organisms, 
are  really  the  distant  results  of  variations  that  were 
aboriginally  induced  in  their  unicellular  ancestors  by 
the  direct  action  of  surrounding  conditions  of  life. 

1  think  it  will  be  well  to  conclude  by  briefly  sum- 
marising the  main  features  of  this  elaborate  theory. 

Living  material  is  essentially,  or  of  its  own  nature, 
imperishable;  and  it  still  continues  to  be  so  in  the 
case  of  unicellular  organisms  which  propagate  by 
fission  or  gemmation.  But  as  soon  as  these  primitive 
methods  of  propagation  became,  from  whatever 
cause,  superseded  by  sexual  it  ceased  to  be  for  the 
benefit  of  .species   that  their  constituent    individuals 


f\ 


'i^  i 


:hi: 


....,  -n;  ,;| 
•  •  •  ■       il' 


II 


■i  -11 1l 


!  I'liilj 


!i4 


24      ^/2  Exa7iiination  of  Weismannism. 

should  be  immortal  ;  seeing  that,  if  they  continued 
to  L  so,  all  speciesofsexually-rcproducinc^  organisms 
would  sooner  or  later  have  come  to  be  composed  of 
broken-down  and  decrepit  individuals.  Consequently, 
in  all  sexually-reproducing  or  multicellular  organisms, 
natural  selection  set  to  work  to  reduce  the  term  ol 
individual  lifetimes  within  the  narrowest  liniits  that 
in  the  case  of  each  species  were  compatible  with  thp 
procreation  and  the  rearing  of  progeny.  Nevertheless, 
in  all  these  sexually-reproducing  organisms  the 
primitive  endowment  of  immortality  has  been  re- 
tained with  respect  to  their  germ-plasm,  which  has 
thus  been  continuous,  through  numberless  genera- 
tions of  perishing  organisms,  from  the  first  origin  of 
sexual  reproduction  till  the  present  time.  Now,  it 
is  the  union  of  germ-plasms  which  is  required  to 
reproduce  new  individuals  of  multicellular  organisms 
that  determines  congenital  variations  on  the  part  of 
such  organisms,  and  thus  furnishes  natural  selection 
with  the  material  for  its  work  in  the  way  of  organic 
evolution — work,  therefore,  which  is  impossible  in 
the  case  of  unicellular  organisms,  where  variation 
can  never  be  congenital,  but  always  determined  by 
the  direct  action  of  surrounding  conditions  of  life. 
Again,  as  the  germ-plasm  of  multicellular  organisms 
is  continuous  from  generation  to  generation,  and  at 
each  impregnation  gives  rise  to  a  more  or  less  novel 
set  of  congenital  characters,  natural  selection,  in 
picking  out  of  each  generation  the  congenital  char- 
acters which  are  of  most  service  to  the  organisms 
presenting  them,  is  really  or  fundamentally  at  work 
upon  those  variations  of  the  germ-plasm  which  in 
turn   give   origin    to   these   variations    of   organisms 


Siatanent  of  Weis?nanns  System  {1886).   25 


[hat  we  recognize  as  congenital.     Thorefore,  natural 

^election  has  always  to  wait  and  to  watch  for  such 

variations   of  germ-plasm    as   will    eventually   prove 

)cncficial    to    the   individuals    developed    therefrom, 

livho  will  then  transmit  this  peculiar  quality  of  gcrm- 

)lasm  to  their  progeny,  and  so  on.     Therefore  also — 

ind  this    is   most    important    to   remember — natural 

selection  as  thus  working  becomes  the  one  and  only 

:ause  of  organic    evolution    in  all  the    multicellular 

)rganisms,  just  as  the  direct  action  of  the  environ- 

lent    is  the  one    and    only  cause    of  it  in  the  case 

)f  all  the  unicellular  organisms.     But  inasmuch  as  the 

multicellular  organisms  were  all  in  the  first  instance 

lerived  from  the  unicellular,  and  inasmuch  as  their 

rerm-plasm    is    of   so    stable    a    nature    that  it  can 

icver  be  altered  by  any  agencies  internal  or  external 

to   the   organisms   presenting    it,  it  follows  that  all 

:ongcnital   variations   are   the    remote   consequences 

)f  aboriginal    differences  on  the    part  of  unicellular 

mcestors.     And,    lastly,    it    follows   also    that    these 

bongenital  variations — although    now  so  entirely   in- 

Idependent  of  external  conditions  of  life,  and  even  of 

'activities    internal    to    organisms    themselves — were 

loriginally  and  exclusively  due    to  the    direct   action 

lof  such    conditions    on  the  lives  of  their  unicellular 

[ancestors ;  while  even  at  the  present  day  no  one  con- 

[gcnital  variation  can  arise  which    is    .lot    ultimately 

luuc  to  differences  impressed  upon  the  protoplasmic 

[substance  of  the  germinal  elements,  when  the  parts 

of  which  these  r  re  non^  composed  constituted  integral 

[parts  of  the  protozoc^,  which  were  directly  and  differ- 

[entially  affected  by  their  converse  with  their  several 

Icnvironments. 


m 


m^ 


..-iil! 

c 

•  f  t  1 1  ;i 

•  «      t       I  ' 

•  * 

t      •      (         . 

t  , 

•  : 

I   -.    ■ 

c      ■ 

'■        «  1   ■■■ 

'  i  ill 


■i 


26      ^«  Examination  of  IVeismanuism. 

Again,  if  for  the  sake  of  distinctness  we  neglect 
all  these  far-reaching  deductions  from  his  theory  ofj 
heredity  whereby  Weismann  constructs  this  elaborate! 
theory  of  organic  evolution,  and  fasten  our  attentionj 
only  upon  the  former,  we  may  briefly  summarize  thel 
fundamental  difference  between  his  theory  of  /ieredii)\ 
and  Darwin's  theory  of  heredity  thus. 

Darwin's  theory  of  heredity  is  the  theory  of  Pan\ 
genesis :  it  supposes  that  a/i  parts  of  the  organisrnj 
generate  anew  in  every  individual  the  formative! 
material  which,  when  collected  together  in  the  germ-j 
cells,  constitutes  the  potentiality  of  a  new  organism] 
and  that  this  new  organism,  when  developed,  resembles! 
its  parents  simply  because  all  the  formative  material! 
in  each  of  the  parents  has  been  'Caw^  generated  hy^Tixm 
collected  from,  all  parts  cf  their  respective  bodies, 
Weismann's  theory  of  heredity,  on  the  other  hand,  isj 
the  theory  of  the  Continuity  of  Gervi-plasm:  it  supposes! 
that  no  part  of  the  parent  organism  generates  atiy  Ci\ 
the  formative  material  which  is  to  constitute  the  newj 
organism ;  but  that,  on  the  contrary,  this  material! 
stands  to  all  the  rest  of  the  body  in  much  the  samel 
relation  as  a  parasite  to  its  host,  showing  a  life  indel 
pendent  of  the  body,  save  in  so  far  as  the  body  supplie?! 
to  it  appropriate  lodgement  and  nutrition  ;  that  inj 
each  generation  a  small  portion  of  this  substance  isj 
told  off  to  develop  a  new  body  to  lodge  and  nourishj 
the  ever-growing  and  never-dying  germ-plasm — this 
new  body,  therefore,  resembling  its  so-called  parent! 
body  simply  because  it  has  been  developed  from  one! 
and  the  same  mass  of  formative  material  ;  and,  lastly, 
that  this  formative  material,  or  germ-plasm,  has  beenj 
continuous    through   all   generations   of  successively 


'anntsm. 

ess  we  neglect! 
I  his  theory  of! 
3  this  elaboratej 
1  our  attention 
summarize  the! 
sory  of  hen'dim 


statement  of  Wcismanns  System  (i8S6).   27 

[rishing  bodies,  which  therefore  stand  to  it  \n  much 
same  relation   as  annual   shoots  to   a  pcicnnial 
?in  :     the     shoots    resemble    one    another    simply 
[cause  they  are  all  grown  from  one  and  the  same 

)ck. 


m 


theory  of  Pan- 
f  the  organism! 

the  formative! 
2r  in  the  germ- 
new  organism; 
3ped,  resembles! 
native  material! 
ncratcd  by,  and! 
pective  bodies, 

other  hand,  isj 
sm :  it  supposes! 
merates  any  olj 
ititute  the  nevj 
,  this  material! 
nuch  the  samel 
ng  a  life  indej 
e  body  suppHesj 
rition  ;  that  inj 
is  substance  ij 
ge  and  nourish! 
m-plasm — thisj 
o-called  parentl 
Dped  from  one! 
al  ;  and,  lastly] 
lasm,  has  bcenl 
^f  successively 


H 


1 

■J. 

.1; 

i 

f 

c 

i 

1 

I  I 


'i!  ii 


;  • 


CHAPTER   II. 

Later  Additions  to  Wkismann's  System 
UP  to  the  year  189a. 

I  HAVE  now  i  1  '  ed  as  complete  a  rhinn^  as  | 
seems  desirable  for  i.  .  sent  pur[)oses  of  Weismann'sj 
theory  of  germ-plasm,  considered  both  as  a  theory  | 
of  heredity  and  as  a  sequent  theory  of  organic 
evolution.  But  before  proceeding  to  examine  this] 
elaborate  system  as  a  whole,  I  must  devote  another] 
chapter  to  a  further  statement  of  certain  later 
additions  to — and  also  emendations  of — the  system 
as  it  was  originally  propounded.  These  additions 
and  alterations  have  reference  only  to  the  theory  of 
heredity:  they  do  not  affect  the  theory  of  organic 
evolution  as  originally  deduced  therefrom.  More- 
over they  have  all  been  due  to  our  more  recently 
acquired  knowledge  touching  the  morphology  and 
physiology  of  cell-nuclei :  it  is  for  the  purpose  of 
bringing  his  theory  of  germ-plasm  into  accord  with 
these  results  of  later  researches  that  Weismann  has 
thus  modified  the  theory  as  it  originally  stood.  For 
my  own  part,  I  do  not  see  that  very  much  is  gained 
by  these  newer  additions  and  modifications  ;  but,  be 
this  as  it  may,  they  are  certainly  very  complicated, 
and  on  this  account  I  have  thought  it  best  to  devote  a 
separate  chapter  to  their  consideration.     Furthermore, 


Later  Additions  tip  to  the  year  1892.    29 


ertain    later  I 


not  only  in  the  opinion  of  Weismann  himself,  but  also 
in  that  both  of  his  friends  and  foes,  the  main  qucsUon 
with  which_hjs_.iatcr  cssays_are_conccrncd — viz..  as  to 
whether  the  nucleus  of  a  cell  is  the  only  part  of  a  cell 
which  is  concerned  in  the  phenomena  of  heredity — is 
regarded  as  of  fundamental  importance  to  his  entire 
edifice.  Hence,  although  I  cannot  myself  perceive 
that  the  indisputable  importance  of  this  question  to 
any  speculations  on  the  subject  of  heredity  is  of  such 
special  or  vital  significance  to  Weismann's  theory,  it 
becomes  necessary  for  me  to  supply  this  further 
chapter  for  the  purpose  of  presenting  the  further 
developments  of  his  theory. 

First  of  all,  Weismann  has  of  late  years  considerably 
modified  his  original  view  touching  the  relation  of 
germ-cells  to  body-cells.  For  while  he  originally 
supposed  the  fundamental  distinction  in  kind  to  obtain 
as  between  the  whole  contents  of  a  germ-cell  and  the 
whole  contents  of  a  somatic-cell,  he  now  regards  this 
distinction  as  obtaining  only  between  the  nucleus  of 
a  germ-cell  and  tne  nucleus  of  a  somatic-cell.  In 
other  words,  he  regards  the  whole  of  a  germ-cell,  with 
the  exception  of  its  nucleus,  as  resembling  the  whole 
of  any  other  cell,  with  the  exception  of  its  nucleus. 
It  is  the  nucleus  of  a  germ-cell  alone  that  contains 
germ-plasm  :  all  the  rest  of  such  a  cell  being  "'  nutritive, 
but  not  formative." 

This  transference  of  the  peculiar  or  hereditary 
powers  of  a  germ-cell  from  the  cell  as  a  whole  to 
the  nucleus,  necessitates  certain  emendations  of  the 
original  theory  of  germ-plasm.  In  particular,  the 
broad  distinction  between  the  whole  contents  of 
a  germ-cell  as  "germ-plasm,"'  and  the  whole  contents 


30      An  Exanmiaiion  of  Weisnianmsm. 


.') 


il 


'I 


:  J 


%• 


of  a  somatic-cell  as  "  somato-plasm,"  is  now  discarded; 
and  in  its  stead  we  have  all  nuclear  matter  (whether 
of  <,rcrm-cclls  or  somatic-cells)  comprised  under  the  one 
denomination  of  "  nucleo-plasm,"  in  contradistinction 
to  all  the  other  protoplasm  of  a  cell,  which  is  called 
'*  cytoplasm."  Hence  VVeismann  now  regards  the 
cytoplasm  of  a  germ-cell  as  identical  with  the  cytoplasm 
of  all  other  cells.  Its  function  is  merely  that  of 
"  nourishing-  "  the  nucleus,  while,  on  the  other  hand,  it 
is  '•  controlled  "  by  the  nucleus  as  to  its  own  growth, 
shape,  size,  and  eventual  division. 

But  it  is  evident  that  the  nucleo-plasm  of  a  germ-cell 
must  differ  from  the  nucleo-plasm  of  a  somatic-cell,  in 
that  it  not  only  "  controls  "  the  growth,  &c.  of  its  own 
cell,  but  likewise  presents  all  the  additional  characters 
peculiar  to  a  germ-cell.  That  is  to  say,  the  nucleo- 
plasm of  a  germ-cell  resembles  the  nucleo-plasm  of 
a  somatic-cell  in  that  it  is  nourished  by,  and  exercises 
control  over,  the  cytoplasm  of  its  own  particular  cell  ; 
but  it  differs  from  the  nucleo-plasm  of  a  somatic-cell 
in  admitting  of  fertilizaJou,  in  the  capability  of 
reproducing  an  entire  organism,  in  the  endowing  of 
that  organism  with  all  its  hereditary  characters,  and. 
lastly,  in  providing  for  its  own  reproduction  in  the  next 
generation. 

Thus  it  is  evident,  as  Weismann  puts  it,  that  the 
nucleo-plasm  of  a  germ-cell  must  be  of  tivo  kinds — 
one  being  concerned  with  the  formation  and  control  of 
the  germ-cell  only,  while  the  other  has  to  do  with  the 
construction  of  an  entire  future  organism,  and  the  sub- 
sequent reproduction  thereof.  But  not  only  so;  for  at 
each  stage  in  the  construction  of  this  future  organism, 
all  the  somatic-cells,  as  successively  constructed,  must 


Later  Additions  np  to  the  year  1892.    ;^i 

likewise  contain  nucleo-plasm  in  two  kinds — one  havin^^ 
to  do  only  with  the  formation  and  control  of  its  own 
individual  cell,  and  t'lie  other  havini^  to  do  with  the 
formation  of  the  future  somatic-cells,  which  will  have 
to  follow  in  the  course  of  ontogeny.  Therefore,  in 
order  to  desit^nate  this  second  kind  of  nucleo-pkism 
(whether  in  a  germ-cell  or  a  somatic-cell)  VVeismann 
borrows  from  Niigeli  the  term  "  idio-plasm  \"  or  rather, 
I  should  say,  he  uses  the  term  "  nucleo-plasm  "  when 
he  is  speaking  of  11  the  contents  of  a  nucleus  indis- 
criminately, while  he  uses~nTeTcFm  "  idio^jilasm  "  when 
he  has  occasion  to  speak  specially  of  the  two  kinds  of 
nucleo-plasm  now  before  us. 

H  nee,  the  nuclear  contents  fnucleo-plasm)  of  every 
cell,  whether  germinal  or  somatic,  present  two  sub- 
stances, which  we  may,  in  the  absence  of  any  better 
terms  supplied  by  Wcismann  himself,  respectively 
designate  "idio-plasm- A"  and  ''idio-plasm-B."  Idio- 
l)lasm-A  is  the  substance  which  has  to  do  only  with 
the  formation  and  control  of  the  individual  cell  in 
which  it  resides,  like  a  mollusc  in  its  shell.  Idio- 
plasm-B  is  the  substance  out  of  which  future  cells 
are  to  be  formed  and  controlled,  when  in  due  course 
either  of  ontogeny  or  phylogeny  this  idio-plasm-]^ 
becomes  converted  into  idio-plasm-A, — i.e.,  into  each 
subsequently  developing  tissue  or  organism,  as  the  case 
may  be.  I  say  ontogeny  or  phylogeny,  and  tissue 
or  organism,  because,  where  a  gcrni-ccll  is  concerned, 
idio-plasm-B  is  capable  of  reproducing  entire  organ- 
isms of  its  own  and  of  subsequent  generations ;  whereas, 

'  The  mc.ininc;  of  this  term,  however,  as  ori^in.illy  used  by  Nii^eli, 
he  so  j,'rcatly  chanties  to  suit  tlic  rcquiiciiicnls  ot  liis  own  theory,  that 
1  thinic  it  would  have  been  better  had  he  coined  some  new  one. 


i 


w 


u:  I 


32 


An  Exaunnatiou  of  Wcismannism. 


', 


in  the  case  of  all  Sflmatic  ccWs,  idio-plasm-B  is  capable 
only  of  reproducirif^,  stai^e  by  stage,  some  greater  or 
less  number  of  the  cells  which  are  to  construct  the 
single  organism  of  which  they  form  a  part.  Or,  other- 
wise expressed,  in  the  particular  case  of  a  germ-cell 
idio-plasm-B  is  germ-plasm,  and  therefore  is  alone 
capable  of  producing  an  entire  organism  of  somatic- 
cells,  while  it  is  likewise  alone  capable  of  reproducing; 
successive  organisms ;  for  it  alone  contains  the 
carriers  of  heredity  ^ 

Thus,  idio-plasm-B  of  an  unscgmented  germ- 
nucleus  is  germ-plasm.  Ikit  as  soon  as  the  germ- 
nucleus  has  undergone  its  first  nuclear  division,  its 
nucleo-plasm  is  no  longer  germ-plasm,  inasmuch  as 
each  of  the  half-portions  is  now  no  longer  capable  of 
reproducing  an  entire  organism — un!  ss  it  be  in  the 
case  of  identical  twins.  Similarly  in  the  second  nuclear 
division,  each  of  the  four  resulting  idio-plasms-B  is 
still  further  removed   from   the  pristine  character  of 

'  I  think  it  is  to  be  ro<;rctted  that  for  this  other  kind  of  iclio-plasni 
(i.e.,  idio-plasm  l'>)  Weismann  has  not  coined  some  distinctive  name, 
or  some  distinct:  c  jirefix,  such  as  that  which  he  sometimes  employs  whtii 
speaking  of  tlie  other  kind  (i.e.,  idio-plasm- A' — viz.,  '•somatic-idio- 
plasm." Also,  the  interchanyi-able  manner  in  which  he  uses  his  term 
"idio-plasm"  with  the  term  "  nuclco-plasm,"  is  somewhat  confusing 
(e.g.,  pp.  217,  219,  220,  250,  251,  &c.  .  I  may  add  that  the  word 
"plasm"  in  all  its  combinations  appears  to  me  an  unfortunate  one, 
since  it  seems  to  betoken  a  substance  tliat  can  be  seen,  instead  of  merely 
inferred.  13ut,  be  this  as  it  may,  the  following  table  of  terms  employed 
may  be  u?:eful  for  ready  reference  :  — 

Nucleo-plasm    =  the  whole  contents  of  the  nucleus  of  any  cell. 
Cytoplasm  =  all  tlie  other  contents  of  any  cell. 

Idio-plasra-A    =  that  juntion  ol  nucleo-plasm  whicli  "  controls"  a  single 

cell. 
Idio-plasm  1j     =  that   portion  of  nucleo-plasm  which  is  destined  tu 

CDiiitruct  future  cells. 
Germ-plasm       =  undifferentiated  idio-plasm-B. 
Somato-plasm   -  idio-plasm  A  +  cyt»)plasm. 


V— --y-^^^^.yywityyB 


imsin. 

■B  is  capable 
e  greater  or 
:onstruct  the 
t.  Or,  othcr- 
"  a  germ-cell 
"ore  is  alone 
of  somatic- 
reproducing 
ontains    the 

tited  germ- 
>  the  germ- 
division,  its 
n  as  much  as 
r  capable  of 
it  be  in  the 
:ond  nuclear 
^lasms-B  is 
aracter  of 

of  idio-plasm 

•<tinctive  nnnif, 

employs  whLii 

somatic-idio- 

uses  his  term 

lat  confusing; 

lat   tlie   word 

forlunatc   one, 

lead  of  merely 

rms  employed 

cell. 

:rols"asin;,'le 

destined  tu 


Later  Addiiions  up  to  the  year  1892. 


1  ■> 


i-plj 


and 


through  all 


lasm  ;  ana  so  on  tnrougn  an  successive  stages 
of  segmentation.  Hence  these  successive  nuclear 
divisions  must  indicate  a  partitioning  and  re-par- 
titioning of  the  original  idio-plasm-B  (germ-plasm) 
into  the  idio-plasms-B  severally  distinctive  of  all  the 
various  cells  of  the  soma. 

Now,  it  is  evident  that  not  all  the  idio-plasm-B  of 
a  germ-cell  which  thu.;  passes  over  into  the  nuclei  of 
somatic-cells  can  be  represented  by  the  itlio-plasm-li 
of  those  cells.  At  every  stage  of  successive  cell- 
formation  a  certain  part  of  the  original  idio-plasm-B  of 
the  germ-cell  must  become  the  idio-plasm-A  of  somatic- 
cells  distinctive  of  that  stage.  For,  supposing  that  at  its 
differentiation  stage  99  the  original  germ-plasm  (now 
somatic-idio-plasm-B  of  99th  stage)  has  reached  a 
phase  of  ontogeny  where  the  formation  of  tissue  ;//  has 
next  to  be  followed  by  the  formation  of  tissue  «,  then 
there  still  remain  the  further  differentiation  stages  101, 
102,  103,  &c.,  to  be  provided  for,  vdiich,v/hen  their  time 
arrives,  will  go  to  form  the  still  later  tissues^,/,  q,  &c. 
Consequently  the  idio-plasm-B  of  stage  100  cannot  be 
rt// consumed  in  making  the  tissue  n.  There  must  be 
a  residual  portion  which  will  afterwards  be  called  upon 
to  form  successively  the  idio-plasm-A  of  o,  p,  q,  &c. 
Where,  then,  is  this  residual  portion  of  idio-plasm 
posited  ?  Clearly  it  must  be  posited  in  the  nuclei 
of  n.  Thus  it  is  that,  as  we  began  by  stating,  all  the 
nuclei  of  any  given  tissue  n  really  contain  two  kinds  of 
substance, — ( 1 )  their  own  idio-plasm-A,  which  was  part 
of  idio-plasm-B  of  the  preceding  tissue,  w;  and  (2)  the 
idio-plasm-B,  which  is  destined  to  become  idio-plasms- 
A  of  succeeding  tissues  o,p^  q,  &c.  Thus  it  follows  also 
that  the  more  the  original  idio-plasm-B  is  differentiated 

D 


if 


! 


i.    II 
,--     It 


II 


34      An  Examination  of  Weismannism. 

into  these  successive  formations  of  idio-plasms-A  the 
less  of  it  remains  for  further  dificrentiation,  till,  at  the 
last  stage  of  ontogeny,  all  the  original  idio-plasm-B 
(germ-plasm)  has  been  thus  changed  into  idio-plasms-A 
severally  distinctive  of  all  the  somatic-tissues  a,  b,  c 
— x,y^  5^,— save  only  the  portion  of  it  which  has  been 
carried  through  all  these  ontogenetic  stages  in  a 
wholly  «;/differentiated  condition,  for  the  purpose  of 
securing  the /!'//;'A;^^;/i7/V  production  of  the  next  gener- 
ation. And  this,  of  course,  is  secured  by  the  portion  of 
undifferentiated  gorm-plasm  in  question  being  de- 
posited in  the  nuclei  of  germ-cells,  at  whatever  stage  of 
the  ontogeny  these  may  be  formed. 

Finally,  it  is  evident  that,  at  each  stage  of  the 
differentiation  of  idio-plasm-B  into  idio-plasms-A, 
the  portion  concerned  must  be  capable  of  self-multi- 
plication to  an  almost  incalculable  extent, — yet  this 
only  as  idio-plasm-B  of  the  particular  kind  required  for 
constructing  the  idio-plasm-A  which  is  appropriate  to 
the  particular  stage.  Such  is  a  necessary  deduction 
from  the  terms  of  Weismann's  theory,  inasmuch  as  we 
know  that  at  each  of  the  ontogenetic  stages  there  i.s 
an  incalculable  multiplication  of  cells  belonging  to  that 
stage — cells,  the  "  cytoplasm  "  of  which  necessarily 
presupposes  for  its  formation  its  own  appropriate 
idio-plasm  in  both  kinds,  and  this  in  similarly  increased 
quantities. 

From  the  above  theory  it  follows  that  an  explana- 
tion can  be  given  of  the  healing  of  wounds  (as  in 
ourselves),  of  the  regeneration  of  lost  parts  (as  the 
limb  of  a  newt),  or  even  of  the  reproduction  of  an 
entire  organism  from  a  mere  fragment  of  somatic- 


Later  Additions  tip  to  the  year  1892.    35 

tissue  ''as  in  the  cases  already  alluded  to  at  the  com- 
mencement of  this  chapter — viz.  the  leaf  of  Begonia, 
portions  of  sea-anemones,  jelly-fish,  &c.).  For  in 
all  these  cases  of  repair,  regeneration,  and  what  may 
be  called  somatic  reproduction,  we  have  only  to  suppose 
that  not  all  the  idio-plasm-B  of  any  given  ontogenetic 
stage  is  consumed  in  the  formation  of  that  stage,  and 
therefore  that  the  residue  is  passed  on  to  the  later 
stages  in  a  latent  condition.  It  will  then  be  avail- 
able at  any  time  to  re-develop  tissue  corresponding 
to  that  particular  stage,  should  that  particular  tissue 
happen  to  be  lost  by  accident  or  disease.  For  example, 
if  some  of  the  idio-plasm-B  of  the  very  first  onto- 
genetic stage,  or  true  germ-plasm,  should  thus  be 
passed  on  in  an  undifferentiated  condition  through 
the  somatic-tissues  subsequently  formed  at  later  onto- 
genetic stages,  then  we  can  understand  why  an  entire 
organism  is  reproduced  from  a  fragment  of  these 
tissues — or  of  those  among  which  particles  of  such 
residual  and  undifferentiated  germ-plasm  happen  to 
be  scattered.  Similarly,  if  idio-plasm-B  of  the  onto- 
genetic stage  at  which  a  limb  is  formed  be  not  all 
consumed  in  constructing  the  limb,  then  the  limb, 
if  afterwards  lost,  will  be  re-constructed,  although  an 
entire  organism  will  not  be  reproduced  from  a  frag- 
ment of  somatic-tissue.  And  similarly  also  with  the 
mere  repair  of  injuries,  where  the  only  overplus  of 
idio-plasm-B  is  that  of  idio-plasm-B  belonging  to  the 
very  last  stages  of  ontogeny. 

But,  it  is  almost  needless  to  observe,  this  kind  of 
transmission  of  idio-plasm-B  from  one  stage  of  on- 
an  unaltered  condition  tc 


)geny 


ibsequent  stages 


is  not  to  be  confused  with  the  other  kind  of  trans- 

D   2 


; 


36      An  Exiifni nation  of  Weismannisju. 

inission  previously  referred  to,  whereby  idio-plasm-I5 
of  one  stajTc  becomes  successively  transformed  into 
the  idio- plasms -A  of  successive  stages.  In  the 
former  case,  at  whatever  sta^^e  of  ontogeny  the 
transnn'ssion  may  start  from,  the  idio-plasm-B  from 
that  stage  lies  dormant,  and  is  never  destined  to 
undergo  further  differentiation,  unless  the  results  of 
accident  or  disease  should  call  upon  it  to  do  so.  In 
the  latter  case,  on  the  other  hand,  the  idio-plasm-B 
of  any  given  stage  is  passed  on  to  the  next  stage 
for  the  ex[)ress  purpose  of  trani^forming  itself  into 
the  idio -plasms -A  of  that  and,  in  due  order,  of  all 
subsequent  stages. 

It  will  be  observed  that  all  this  elaboration  of  the 
original  theory  a  germ-plasm — an  elaboration  which 
is  largely  derived  from  the  speculative  writings  of 
Niigeli — serves  no  other  purpose  than  that  of  indicating 
what  Professor  Weismann  now  regards  as  the  most 
probable  mode  in  which  germ-plasm  undergoes  its 
modification  into  the  various  kinds  of  somatic-cells. 
For,  inasmuch  as  the  idio-plasms-B  of  all  somatic-cells 
are  originally  derived  from  that  of  the  germ-cell,  and 
inasmuch  as  each  expends  its  formative  energies 
exclusively  in  constructing  and  controlling  the  cells 
which,  as  idio-plasms-A,  they  respectively  inhabit,  it 
is  still  the  germ-plasm  of  the  original  germ-cell  that 
is  finally  converted  into  the  various  tissues  which 
together  constitute  the  soma  — notwithstanding  that, 
in  order  thus  to  become  transmuted  into  body-sub- 
stance, or  somato-piasm.i'c  must  pass  through  the  sundry 
intermediate  stages  of  idio-plasm-B,  idio-plasm-A,  and 
cytoplasm,  of  any  given  ontogenetic  stage.     Hence 


Later  Additions  up  to  the  year  1892.     37 

I  do  not  see  that  it  makes  any  substantial  difference  to 
Weismann's  theory  of  heredity,  whether  we  speak  of 
germ-pkism  being  converted  into  "  somato-plasm," 
or  into  "  idio-plasm  "  phis  "  soniatic-idio- plasm,"  phis 
*'  cytoplasm."  But  as  Weismann  himself  thinks  that 
it  does  make  some  great  difference  whether  we  adhere 
to  his  original  generic  term  "  somato-plasm,"  or  adopt 
his  newer  and  more  specific  terms  as  just  enumerated, 
I  append  in  extenso  the  most  recent  exposition  of  his 
views  upon  this  subject  \ 

Before  quitting  this  somewhat  complicated  addition 
to  the  original  theory  of  germ-plasm,  I  must  briefly 
allude  to  the  descriptions  and  illustrations  of  karyo- 
kinesis  which  were  given  in  Part  I  of  Darivin  and  after 
Darwin^  for  the  prospective  benefit  of  any  general 
re.'  '?rswho  might  afterwards  be  sufficiently  interested 
i)  Hsmann's  speculations  to  desire  a  statement  of 
the  main  facts  on  which  this  further  development  of  his 
theory  rests.  It  seemed  undesirable  to  burden  the 
present  volume  with  an  account  of  recent  investigations 
so  well  known  to  naturalists,  while,  on  the  other  hand, 
it  was  clearly  desirable  that  such  an  account  should  be 
given  somewhere,  if  the  speculations  in  question  were 
to  be  rendered  intelligible  to  anybody  else.  There- 
fore I  must  here  request  those  of  my  readers  who  are 
not  already  acquainted  with  the  matter  to  consult 
pp.  J2(S-i34  of  Part  I.  It  will  there  be  seen  how 
enormously  complex  are  the  visible  processes  which 
take  place  in  the  nucleus  of  a  germ-cell  (and  likewise 
of  a  somatic-cell),  preparatory  to  its  division  ;  and 
therefore,  supposing  that  the  nucleus  alone  contains 
the  material  concerned  in  the  phenomcma  of  heredity, 

'  See  close  of  Appendix. 


i't 


I  'i: 


jjl'. 

■ffi^^Jf  1 

Bk  '       '4  j 

I  :  I 


'1 1 


'■  I 


I  I  « 


•4      i'li 


38       An  Examination  of  Weistnannism, 

it  appears  that  no  small  corroboration  is  lent  to  Weis- 
maniis  views  by  these  histological  observations.  And, 
more  particularly,  if  we  suppose  with  him  that  the 
material  in  question  is  restricted  to  that  portion  ot 
the  segregating  nuclear  matter  which  is  called  the 
"  nuclear  thread  ^"  in  t.'ie  formation  of  the  "  loops  " 
or  "  rods  "  of  this  substance  we  seem  to  have  pre- 
sented a  visible  expression  of  the  marshalling  of  "the 
carriers  of  heredity,"  and  the  successive  passage  of  the 
originally  generalized  "germ-plasm"  of  the  germ-eel) 
into  the  ever  more  and  more  specialized  "nucleo- 
plasms" of  the  somatic-cells.  Indeed,  the  new  theory 
of  heredity,  when  thus  brought  into  relation  with  the 
new  results  of  histological  observation,  appears  so  well 
to  fit  the  latter,  that  one  would  be  sorry  to  find 
the  coincidence  unmeaning,  or  the  theory  false.  I^ut. 
without  passing  any  criticism,  it  is  sufficient  to  note 
that  the  question  whether  or  not  the  theory  is  true — 
and  therefore  correctly  interprets  the  phenon.cna  of 
karyokinesis, — must  depend  chiefly  on  whether  it 
be  eventually  proved  that  the  **  nuclear  thread "  is 
indeed  the  only  part  of  a  germ-cell,  or  even  the 
only  part  of  a  tissue-cell,  which  is  concerned  in  con- 
trolling the  plicnomena  of  heredity  on  the  one  hand, 
and  of  ontogeny  on  the  other.  Into  this  v^uestion, 
however,  I  do  not  propose  tc  enter.  It  will  be  enough 
to  assume,  for  the  sake  of  argument,  that  Weismann's 
view  of  the  matter  will  eventually  prove  to  be  true. 
At  the  same  time,  w  must  remember  that  at  present 
this   view  as   to  the  nuclear  thread  being  the  sole 

*  See  Part  I,  figs.  .^6,  37,  and  38.  The  substance  of  this  thread,  in 
the  various  phases  of  its  segmentation,  is  the  "  chromatin,"  as  there 
depicted,  and  so  called  because  it  takes  a  stain  better  than  oth-jr  parts 
of  the  nucleus — thus  showing  some  distinctive  character. 


Later  Additions  up  to  the  year  1892.  39 

repository  of  the  material  of  heredity  i,j  merely  hypo- 
thetical. 


We  now  arrive  at  the  last  of  those  features  in 
Weismann's  theory  of  heredity,  the  importance  of 
which  necessitates  mention  in  such  a  mere  statement 
of  the  theory  as  the  present  chapter  is  concerned 
with. 

According  to  Weismann's  own  view  of  his  theory, 
two  objections  have  to  be  met.  In  the  first  place, 
there  is  the  objection  that  all  individuals  :v/ii:h  are 
born  of  the  same  parents  are  not  exactly  alike,  as  the 
theory  might  have  expected  they  would  be,  s»_cing  that 
the  admixture  of  identical  germ-plasms  has  been  con- 
cerneil  in  the  formation  of  the  whole  progeny.  In 
the  second  place,  and  quite  apart  from  this  objection, 
there  Is  the  difficulty  that,  if  every  act  of  fertilization 
essentially  consists  in  a  fusion  of  one  mass  of  germ- 
plasm  belonging  to  a  male  gcrm-ccU  with  another  mass 
belonging  to  a  female  germ-cell,  ot  each  generation 
the  mass  of  germ-plasm  contained  in  on  egg-cell 
mubt  be  doubled — with  the  result  that  ova  must 
progressively  increase  in  size  during  the  course 
of  phylogcny.  ikit  ova  do  not  tlius  progressively 
increase  in  size.  Therefore,  if  the  imperishable  nature 
of  germ-plasm  is  to  be  theoretically  sustained,  it 
is  necessary  to  show  some  means  whereby  ova 
and  spermatozoa  are  able  to  get  rid  of  at  least 
one  half  of  their  respective  germ-plasms  in  each 
generation — i.  e.,  before  each  act  of  impregnation. 
Weismann  meets  both  these  difficulties  by  an  appeal 
to  the  following  facts. 

It  is  well  known  that  the  ripe  ovum  extrudes  two 


40       An  Examination  of  Weismannism. 


Wi 


minute  particles  of  protoplasmic  substance,  which  are 
called  polar  bodies  ^  These  both  proceed  from  the 
nucleus  of  the  ovum,  but  are  not  formed  simul- 
taneously. For  the  first  polar  body  is  really  one 
half  of  the  original  nucleus  of  the  cell,  and  therefore 
is  formed  by  the  first  segmentation  of  this  nucleus. 
The  second  polar  body,  on  the  other  hand,  is  one  half 
of  the  remaining  nucleus,  and  is  similarly  formed 
by  the  second  segmentation.  Hence,  when  both 
polar  bodies  have  been  extruded  from  the  ovum,  only 
one  quarter  of  the  original  nuclear  matter  remains.  So 
far,  of  course,  the  facts  prove  too  much  for  Weis- 
mann's  theory,  because  the  theory  wants  to  get  rid  of 
only  one  half  of  the  original  nuclear  matter  before 
impregnation,  if  all  the  nuclear  matter  be  g'^rvi-plasm. 
Therefore  Weismann  concludes  that  all  the  original 
nuclear  matter  of  the  ripe  ovum  is  not  germ-plasm, 
but  that  only  one  half  of  it  is  so,  while  the  other  half — 
or  that  half  which  goes  to  constitute  the  first  polar 
body — is  idio-plasm-A,,  which,  as  we  have  already 
seen,  the  egg-cell  shares  in  common  with  all  other 
cells.  It  is  merely  "  ovogenetic  "  :  its  function  is  that 
of  constructing  the  ovum,  quA  cell :  it  has  nothing 
whatever  to  do  with  the  germ-plasm  which  the 
parti«-./!arcell  contains.  Therefore,  having  discharged 
its  function  of  constructing  this  cell,  it  is  itself  dis- 
charged from  the  cell  as  the  first  polar  body. 

The  nucleus  of  the  fully-formed  ovum  having  thus 
got  rid  of  all  its  superfluous  idio-nlasm-A  by  throwing 
off  the  first  polar  body,   is  supposed   henceforth   to 

'  For  an  .iccount  of  the  formation  and  expulsion  of  these  bodies,  see 
Part  I,  pp.  125-6.  Tiiere  is  now  no  longer  any  doubt  touching  the 
statement  there  made  as  to  the  n)ale-ccll  likewise  parting  with  some  of 
its  nuclear  substance  prior  to  fertilizing  the  female. 


Later  Additions  up  to  the  year  1892.  41 

consist  of  pure  germ-plasm  (i.  e.,  of  idio-plasm-B 
belonging  to  the  first  ontogenetic  stage),  and  one  half 
of  this  is  next  got  rid  of  by  the  second  segmentation 
in  the  form  of  the  second  polar  body.  Therefore, 
according  to  the  theory  and  so  far  as  the  problems 
of  heredity  are  concerned,  we  need  not  any  further 
trouble  ourselves  about  the  first  polar  body.  But  it 
will  at  once  be  seen  that  by  the  interpretation  which 
Weismann  puts  upon  the  second  polar  body,  and 
also,  of  course,  upon  the  extrusion  of  some  of  its 
nuclear  matter  by  the  male  cell,  he  meets  both  the 
difficulties  against  his  theory  of  germ-plasm  which 
we  are  now  engaged  in  considering. 

That  he  thus  meets  the  second  of  those  difficulties — 
i.  e.,  concerning  the  otherwise  perpetual  accumulation 
of  germ-plasm — is  evident  without  explanation.  That 
he  likewise  meets  the  first — i.  e.,  concerning  the  non- 
resemblance  of  individuals  born  of  the  same  parents — 
is  scarcely  less  evident.  For  it  is  hardly  conceivable 
that  such  a  complex  mass  of  germ-plasms  as  the 
nucleus  of  a  fertilized  ovum  must  be  could  ever 
present  in  any  two  eggs  precisely  the  same  propor- 
tional representation  of  the  "  carriers  of  heredity," 
after  one  half  of  each  set  had  been  thus  discharged 
from  each  ^^g.  Therefore,  if  the  second  polar  body 
removes  from  each  egg  one  half  of  the  ancestral  germ- 
plasms,  "  every  f^gg  will  contain  a  somewhat  different 
combination  of  hereditary  tendencies,  ind  thus  the 
offspring  which  arise  from  the  different  germ-cells  of 
the  same  mother  can  never  be  identical  ^ 

Such,  then,  is  Weismann's  theory  of  the  physio- 

'  In  the  case  of  identical  twins,  both  are  probably  always  produced 
from  the  same  ovum. 


i:  ■ 

if 

t 


I 


I  'i 


:i    '! 


;jfi 


42      An  Examination  of  Weismannism. 

logical  meaning  of  polar  bodies.  And  as  the  bearing 
of  this  particular  theory  on  his  more  general  theory 
of  heredity  does  not  appear  to  me  a  vitally  intimate 
one,  I  think  my  subsequent  examination  of  the  main 
theory  will  be  simplified  if  I  now  proceed  at  once 
to  an  examination  of  the  subordinate  one.  For  by 
doing  this  I  shall  hope  to  show  that  the  bearings  just 
mentioned  are  of  much  less  importance  than  he  repre- 
sents them  to  be  ;  and,  therefore,  that  we  may  hereafter 
proceed  to  consider  his  theory  of  heredity  without  any 
special  reference  to  his  theory  of  polar  bodies. 

To  be,^in  with,  as  regards  the  first  polar  body,  one 
would  like  to  know  more  clearly  why  it  is  necessary 
that  this  residuum  of  merely  "  ovogenetic  idio-plasm" 
(or  idio-plasm-A  of  the  egg-cell)  has  to  be  got  rid 
of  before  the  germ  plasm  can  proceed  to  discharge 
its  physiological  functions.  Seeing  that  both  these 
(hypothetically)  very  different  materials  occur  in  the 
self-same  nucleus,  some  very  delicate  mechanism  must 
be  needed  for  their  separation  ;  and  it  is  not  apparent 
why  such  a  mechanism  should  have  been  evolved, 
rather  than  what  would  have  been  the  simpler  plan  of 
adapting  the  germ-plasm  to  hold  its  own  against  the 
idio-plasm-A,  even  if  one  could  sea  that  any  inter- 
ference between  these  very  different  substances  is  in 
any  way  probable.  Yox  my  own  part,  at  all  events, 
T  cannot  see  why  this  microscopical  atom  of  "  ovo- 
genetic idio-plasm "  should  not  simply  be  left  to 
be  absorbed  among  the  millions  of  cells  that  after- 
wards go  to  form  the  foetus. 

Again,  as  regards  the  second  polar  body,  Weismann's 
theory  of  it  is  framed  to  explain,  {a)  how  the  excess  of 
germ-plasm  is  got  rid  of  in  each  ontogeny,  and  {b^  why 


Later  Additions  up  to  the  year  1892.  43 

the  offspring  of  the  same  parents  do  not  all  precisely 
resemble  one  another.  These,  be  it  observed,  are  the 
only  two  functions  which  Weismann's  theory  of  polar 
bodies  subserves  in  relation  to  his  theory  of  germ-plasm. 
But,  it  appears  to  me,  neither  of  these  functions  is 
necessary,  in  so  far  as  any  requirements  of  the  latter 
theory  are  concerned.  For  surely,  polar  bodies  or  no 
polar  bodies,  there  is  already  a  mechanism  at  work  in 
each  ontogeny  which  is  of  itself  sufficient  to  discharge 
both  these  functions,  and  so  to  anticipate  both  the 
supposed  difficulties  which  the  subsidiary  theory  is 
adduced  to  meet.  The  very  essence  of  ontogeny, 
as  a  process,  itself  consists  in  a  continuous  succession 
of  nuclear  divisions — and  this  not  only  as  regards 
sovnatic-cells,  but  also  as  regards  germ-cells.  Now,  in 
the  great  majority  of  organisms,  there  is  an  infinitely 
greater  number  of  germ  cells  (both  male  and  female) 
than  can  possibly  be  required  either  for  the  purpose 
of  getting  rid  of  any  excess  of  germ-plasms  in  the 
nucleus  ol  each  cell,  or  of  preventing  the  germ-plasms 
of  any  one  germ-cell  precisely  resembling  those  of 
any  other.  If  every  plant  or  animal  produced  only 
a  single  female-cell  or  a  single  male-cell,  then  indeed 
we  might  require  from  Professor  Weismann  a  demon- 
.stration  of  some  special  mechanism  to  secure  the  ex- 
pulsion of  half  its  ancestral  germ-plasms  ;  since  other- 
wise the  single  female-cell  or  male-cell  would  have  to 
increase  its  dimensions  in  each  successive  generation. 
But,  as  matters  actually  stand,  nature  seems  to  have 
made  much  more  than  ample  provision  for  prevent- 
ing the  undue  accumulation  of  ancestral  germ-plasms 
in  any  individual  germ-cell,  by  enormously  multiply- 
ing, through  continuous  division  and  subdivision,  the 


%      ! 


!  I' 


44      An  Examination  of  Weismannism. 

number  of  germ-cells  in  each  ontogeny.  And  simi- 
larly, of  course,  as  regards  the  different  aggregations  of 
ancestral  germ-plasms  which  are  left  for  distribution 
among  these  innumerable  germ-cells.  "  If  one  group 
of  ancestral  germ-plasms  is  expelled  from  one  ^^^^ 
and  a  different  group  from  another  Q^'g,  it  follows 
that  no  two  eggs  can  be  exactly  alike  as  regards  their 
contained  hereditary  tendencies."  Granted  ;  but  this 
consideration  applies  equally  to  the  original  segre- 
gation of  germ-plasms  in  the  multiplying  eggs  of  each 
ontogeny — for  it  follows  from  the  theory  of  germ- 
plasm  that  the  most  primitive  egg-cell  in  each  ontogeny 
must  have  contained  all  the  ancestral  germ-plasms 
which  are  afterwards  distributed  among  its  innumer- 
able progeny  of  egg-cells.  And,  as  far  as  the  facts  of 
"  individual  variation  "  are  concerned,  I  do  not  see  why 
the  differential  partitioning  of  "  ancestral  idio-plasms" 
should  be  any  better  secured  by  nuclear  division  ot 
a  mature  germ-cell  than  by  that  of  an  immature. 
Less  so,  indeed ;  for  the  wonder  is  that  during 
the  many -thousand -fold  division  of  an  immature 
ovum  so  precise  a  distribution  of  these  "ancestral 
idio-plasms  "  is  maintained,  as  is  proved  to  be  main- 
tained (on  the  theory  of  germ-plasm)  by  the  facts  of 
heredity. 

However,  Weismann  takes  a  widely  different  view  of 
the  matter.  For  while  he  allows  that  "  such  an  early 
reducing  division  would  offer  advantages  in  that 
nothing  would  be  lost,  for  both  the  daughter  nuclei 
would  (?  might)  become  eggs,  instead  of  one  of 
them  being  lost  as  a  polar  body  " — while  he  allows 
this,  he  nevertheless  rejects  the  possibility  of  "  such  an 
early  reducing  division."     But  I  do  not  see  that  the 


, »» 


Later  Additions  ttp  to  the  year  1892.    45 

reasons  which  he  assigns  for  this  rejection  of  it  are 
adequate. 

First,  he  says  that  if  this  were  the  way  in  which  the 
superfluous  germ -plasm  of  each  generation  were  got 
rid  of,  far  too  much  provision  has  been  made  for  the 
purpose, — seeing  that  the  practically  indefinite  number 
of  nuclear  divisions  which  the  immature  germ-cells 
undergo  would  cause  a  much  "  greater  decrease  of 
the  ancestral  idio-plasms  of  each  than  could  afterwards 
be  compensated  by  the  increase  due  to  fertilization." 
But  this  rejoinder  is  of  cogency  only  if  it  be  supposed 
that  at  each  nuclear  division  of  an  immature  ovum, 
"the  ancestral  idio-plasms"  (germ -plasm)  are  in- 
capable of  the  power  of  self-multiplication  which  soon 
afterwards  becomes  one  of  its  most  essential  characters. 
Why,  then,  should  we  suppose  this  substance  to  be 
totally  incapable  of  increase  in  the  multiplying  ova  of 
ontogeny,  when  at  the  same  time  we  arc  to  suppose 
the  same  substance  capable  of  any  amount  of  increase 
in  the  multiplying  ova  of  phylogcny  ?  To  this  obvious 
question  no  answer  is  supplied:  in  fact  the  question 
is  not  put. 

Secondly,  Wcismann  says  that  in  parthenogcnetic 
ova  onlyone  polar  body  is  extruded.  This  he  regards  as 
equivalent  to  the  first  polar  body  of  a  fcrtilizable  ovum 
(i.  e.,  as  composed  of  ovogenetic  nuclear  substance) ; 
and  hence  he  argues  that  the  second  polar  body 
of  a  fcrtilizable  ovum  must  be  regarded  as  composed 
ol  germ-plasm.  But  even  supposing  that  he  is  right 
as  to  the  fact  that  parthenogcnetic  ova  invarir.oly 
extrude  but  one  polar  body,  his  argument  fn  .n  this 
fact  would  only  be  available  after  we  had  already 
accepted    his    view   touching    the   characi:er    of   the 


^1: 


46      An  Examination  of  Weismannism. 

second  polar  body.  So  long  as  this  view  is  itself  the 
subject  of  debate,  he  cannot  prove  it  by  the  fact  in 
question.  In  other  words,  unless  we  have  already 
agreed  that  the  second  polar  body  has  the  function 
which  Weismann  assigns  to  it,  we  cannot  accept  the 
fact  which  he  adduces  as  furnishing  any  evidence  of 
his  view  touching  the  function  of  the  second  polar 
body. 

For  these  reasons  I  cannot  see  that  the  subordinate 
theory  of  polar  bodies  is  required  in  the  interests  of 
the  general  theory  of  germ-plasm.  The  difificulties 
which  it  is  adduced  to  meet  do  not  appear  to  me  to 
be  any  difficulties  at  all.  Therefore,  in  now  proceeding 
to  consider  what  in  my  opinion  are  the  real  difficulties 
which  lie  agairTst  the  major  theory  of  germ-plasm,  I 
shall  not  again  allude  to  the  minor — and,  in  this  con- 
nexion, superfluous — theory  of  polar  bodies. 

Such,  then,  is  Professor  Weismann's  theory  of 
heredity  in  its  original  and  strictly  logical  form.  In 
the  course  of  our  examination  of  it  which  is  to 
follow  in  Chapter  III  and  IV,  we  sli.til  find  that  in 
almost  every  one  of  its  essential  features,  as  above 
stated,  the  theory  has  had  to  undergo — or  is  demon- 
strably destined  to  undergo— someradical  modification. 
But  I  have  thought  it  best  to  begin  by  presenting 
the  whole  theory  in  its  completely  connected  state, 
as  it  is  in  this  way  alone  that  we  shall  be  able  to 
disconnect  what  I  regard  as  the  untenable  parts  from 
the  parts  which  still  remain  for  investigation  at  the 
hands  of  biological  science.  Such,  indeed,  is  the  only 
object  of  my  "  Examination  of  Weismannism."  For, 
rightly  or  wrongly,  it  appears  to  me  that  the  unques- 
tionable value  of  his  elaborate  speculations  is  seriously 


;  -M 


Later  Additions  up  to  the  year  1892.    47 

discounted  by  certain  oversights  with  regard  to 
matters  of  fact,  and  not  a  few  inconsistencies  touching 
matters  of  theory.  In  displaying  both  these  defects, 
I  am  not  without  hope  that  the  result  may  be  that 
of  inducing  Professor  Wcismann  so  to  modify  his 
system  of  theories  as  to  strengthen  the  whole  by 
removing  its  weaker  parts. 


?•! 


•-i  n 


ji 


i; !  jj 


CHAPTER    III. 


Wkismann's  theory  of  Heredity  (1H91). 

We  now  proceed  to  examine  Wcismann's  theory  of 
germ-plasm,  and  as  this  in  its  various  developments 
has  now  become  a  highly  complex  theory,  we  had 
best  begin  by  marking  out  the  lines  on  which  the 
examination  will  be  conducted. 

As  I  have  already  pointed  out,  the  Weismannian 
system  is  not  concerned  only  with  the  physiology 
of  reproduction  :  it  is  concerned  also — and  in  an  even 
larger  measure — with  the  doctrine  of  descent.  The 
theory  of  germ-plasm  as  a  whole  is  very  much  more 
than  a  theory  of  heredity;  it  is  a  new  theory  of 
evolution.  The  latter,  indeed,  is  deduced  from  the 
former;  but  although  the  two  are  thus  intimately 
related,  they  are  nevertheless  not  mutually  dependent. 
P^or  the  relationship  is  such  that  the  new  theory  of  evo- 
lution stands  upon  the  basis  supplied  by  the  new  theory 
of  heredity,  and  although  it  follows  from  this  that 
if  the  latter  were  disproved  the  former  would  collapse, 
it  does  not  follow  that  if  the  former  were  to  be  found 
untenable  the  latter  must  necessarily  be  negatived. 
Hence,  for  the  sake  of  clearness,  and  also  for  the 
sake  of  doing  justice  to  both  theories,  we  had  best 
deal  with  them  separately.     The  present  chapter,  then, 


IVcisinauiis  l/icory  of  Heredity  (1891).  49 


will  be  devoted  to  cxaniininj;  VV'eismann's  theory  of 
heredity,  while  the  ensiiinj^  chapter  will  be  concerned 
with  his  sequent  theory  of  evolution, 

Ai^ain,  Weisinann's  theory  of  herctiity  stands  on 
his  fundamental  postulate— the  continuity  of  j,'erni- 
plasm;  and  also  on  a  fact  well  recoj^nized  by  all  other 
theories  of  heredity,  which  he  calls  the  stabilit)'  of 
gerni-plasni.  liut  his  sequent  theory  of  evolution 
stands  not  only  on  this  fundamental  p;istulate  and  an 
this  well-recoL^nized  fact ;  it  requires  for  its  loj.;ical 
basis  two  further  postulates — viz.,  that  ij^erm-plasm 
has  been  perpetually  continuous  ''  since  the  first  origin 
of  life,"  and  imalterably  stable  "since  the  first  ori<^in 
of  sexual  propai^ation."  That  these  things  are  so. 
a  very  few  words  will  be  sufficient  to  prove. 

Any  theory  of  heredity  which  su[)[)()ses  the  material 
of  heredity  to  occupy  a  more  or  less  separ;ite  "  sphere  ' 
of  its  own,  is  not  obliged  further  to  suppose  that  this 
material  has  always  been  thus  isolated,  or  even  that 
it  is  now  invariably  so.  There  have  been  one  or  two 
such  theories  [)rior  to  Weismann's,  and  they  were 
founded  on  the  well-known  fact  of  congenital  characters 
being  at  any  rate  miteJi  more  heritable  than  are 
acquired  characters.  Hut  it  has  not  been  needful  for 
these  theories  to  assume  that  the  "continuity"  thus 
postulated  has  hcQw  perpetnnliy  unbroken.  Even  if  it 
has  been  frequently  to  some  extent  interrupted,  all 
the  facts  of  heredity  could  be  ecjually  well  compri.sed 
under  such  theories — and  this  even  if  it  be  supposed 
that  acquired  characters  are  but  rarely,  or  never, 
transmitted  to  progeny.  T'or,  in  as  far  as  the  con- 
tinuity may  have  been  interrupted,  it  does  not  follow 
that  the  acquired  characters  (body-changes),  which  by 

E 


ill 


i 


11 

1 


50      An  Exatninatiou  of  U\is)itannism. 

hypothesis  caused  the  intcrrir  tioii,  must  be  inherited 
by  progcry  exactly  as  they  occurred  in  the  parents. 
Or,  in  otner  words  and  adopting  VVeismann's  ter- 
niinoIt)gy,  so  far  as  the  fads  if  heredity  are  eeneerned, 
there  is  no  reason  wliy  gerni-plai-'ni  should  not 
frequent!)'  have  had  its  hereditary  qualities  modified 
by  some  greater  or  less  ilcgrec  of  commerce  with 
somatic-tissues,  and  yet  never  have  reproduced  in  pro- 
geny the  identical  acquired  characters  which  caused 
the  modification  of  germ-plasm  in  the  parents  :  some 
other  and  totally  different  characters  might  with  etpial 
— or  even  more — likelihood  have  been  the  result,  as  we 
shall  see  more  clearly  a  few  pages  further  on.  Why, 
then,  does  Weisinatm  so  insist  ui)on  this  continuity  of 
germ-plasm  as  perpetual  '•  since  the  origin  of  iife  "  ?  It 
appears  to  me  that  his  only  reason  for  doing  so  is 
to  provide  a  basis,  not  for  his  theory  of  heredity,  but 
for  his  additional  theory  of  evolution.  It  is  of  no 
consequence  to  the  former  that  germ-i)lasm  should 
be  regarded  as  thus  peri)ctual,  while  it  is  of  high 
importance  to  the  latter  that  the  fundamental  postulate 
of  continuity  should  be  supjjlemcnted  by  this  further 
postulate  of  the  continuity  as  thus  perpetual. 

Similarly  as  rei^ards  the  postul:.te  of  the  stability 
of  germ-plasm  as  absolute.  Il  is  enough  for  all  the 
requirements  of  VVeismann's  theory  of  heredity  that 
the  material  basis  of  heredity  should  present  a  merely 
high  degree  of  stability,  such  as  the  facts  of  atavism, 
degeneration,  &c.  abundantly  prove  that  it  possesses. 
For  his  sequent  theory  of  evolution,  however,  it  is 
necessary  to  postulate  this  stability  as  absolute  "since 
the  first  origin  of  sexual  reproduction."'  Other- 
wise there  would   be   no  loiindation   for  any  of   the 


i<|,    ^^^.^JS^^^-.- 


IVi'isuianns  theory  oj  Ilcndily  (1S91).  51 

distinctive    doctrines    which    go    to    constitute    this 
theory. 

It  may  not  be  immediately  apparent  that  Weis- 
mann's  theory  of  liereih'ty  is  not  per  sc  concerned 
with  eitlier  of  these  two  additional  postulates  of  the 
contimiity  of  ^erm-plasm  as  pcrpctuaL  and  the  stahiHty 
of  i;enn-[)lasm  as  absolnlc\  while  both  are  loL;ically 
necessary  to  his  further  theory  of  evolution.  On  this 
account,  and  als(j  for  the  sake  of  clearness  in  all 
that  is  to  follow,  we  had  best  bi.L;in  b)-  cotn[)arinL^ 
his  thco)}  of  heredity  with  those  of  his  principal 
[)redecessors — Darwin  and  Galton. 

For  the  purposes  of  this  comparison  we  may  start  by 
again  alluding  to  the  fact,  that  even  in  the  multicellular 
organisms  reproduction  is  not  confined  to  the  sexual 
methods.  Many  kinds  of  invertebrated  animals  will 
re  prod  u  CO  entire  organisms  from  the  fragments  into 
which  a  single  organism  has  been  choi)ped  :  plants 
of  various  kintls  can  be  i)ropagateJ  indefinitely  by 
cuttings,  grafts,  and  buds,  or  even  by  leaves,  as  we 
have  already  observed  in  Chapter  I.  Now.  when 
the  whole  organism  is  thus  »eproduced  from  a  severed 
portion  o£  s()matic-tissue,  it  reproduces  its  se.Kual 
elements.  Whence,  then,  in  such  cases  are  these 
elements  derived  ?  Obviously  they  are  not  derived 
immediately  from  the  sexual  organs — or  even  from 
the  sexual  cells — of  their  parents:  they  are  derived 
from  the  somatic-cells  of  a  single  parent,  if  we  choose 
to  retam  this  term ;  and  therefore,  as  Strasburger 
pointed  out  soon  after  Weismann's  theory  was  pub- 
lished, it  seems  as  if  such  facts  arc  in  themselves 
destructive  of  the  theory.     I  low.  then  does  Weismann 

!«:  2 


•i, 
■  1 


If 


X 


IS 


1'^ 

|; 


52       An  Exaniinatiou  of  Weisniannism. 

meet  them?  As  we  have  already  seen  in  Chapter  II, 
he  '.nects  them  in  the  only  way  they  can  be  met  on 
the  lines  of  his  theory — viz.,  by  those  newer  amend- 
ments of  his  theory  which  suppose  that  in  all  these 
cases  the  £]^crm-plasm  is  ;/<;/^n fined. to  the  specially 
sexual  cells,  but  occurs  also  in  the  nuclear  substance 
of  those  somatic-cells  which  thus  prove  themselves 
capable  of  developincj  into  entire  ortj^anisms.  In 
other  words,  the  sexual  ciemcnts  which  develop 
dvirincj  what  I  have  previously  called  this  "somatic 
reproduction"  of  multicellular  organism,  are  supposed 
to  be  derived  from  the  sexual  cells  of  ancestors,  not 
indeed  immediately  (for  this  they  plainly  are  not), 
but  mediately  through  the  somatic-tissues  of  their 
a-sexual  parent.  Now,  in  view  of  this  extension,  the 
theory  cf  germ- plasm  becomes  somewhat  closely 
alTietrto  that  of  pangenesis.  For  example,  when  the 
fragment  of  a  leaf  of  Bci^onia  is  laid  upon  moist  soil, 
there  strikes  root,  and  grows  a  new  Begonia  plant 
capable  of  sexual  reproduction  Darwin  supposes  the 
explanat.ioa..tq  be  that  what  he  calls  "formative 
material"  occurs  in  all  cells  of  the  leaf,  while  Weismann 
supposes  the  explanation  to  be  that  what  he  calls 
"  germ-plasm  "  occurs  in  all — or  at  any  rate  in  most — 
of  the  cells  of  the  leaf.  So  that,  except  as  regards  the 
terms  employed,  the  t.vo  theories  are  identical  in  their 
mode  of  viewing  this  particular  class  of  phenomena. 

Moreover  by  thus  allowing,  in  his  second  essay  on 
Heredity,  that  germ-plasm  need  not  be  restricted  to 
the  specially  sexual  cells,  but  in  some  cases,  at  any 
rate  ^,  may  occur  distributed  in  full  measure  of  repro- 

'  We  have  no  ino.ins  of  esliniatiiii;  exactly  tlic  proportional  number 
of  cases  in  whicii  tliis  is  pussihle,  eitiier  amon^  tlu;  lower  or  the  liigher 


'■T'g  ■«!■'■;««■  .■S'gT 


Weismatms  theory  of  Heredity  (1891).  53 


ductivc  efficiency  throughout  the  general  tissues  of 
the  organism,  VVeismann  cannot  refrain  from  taking 
the  further  step  of  supposing  that  the  germ-plasm, 'li^i  \^  %„w>«^., 
like  the  gemmules  of  Darwin,  is  capable  of  any  /^  ^j^  L^iv, 
amount  of  multiplication  in  tJic  goicral  cellular  tissues 
of  plants — seeing  that  plants  can  be  propagated  by 
cuttings,  buds,  &c.,  indefinitely.  And  this,  as  we  have 
seen,  Professor  VVeismann,  in  his  second  essay,  does 
not  shrink  from  doing.  Moreover,  although  I  cannot 
remember  that  he  has  anywliere  expressly  said  so,  it 
is  obvious  that  the  allied  phenomena  of  regeneration 
and  rejoair  admit  of  explanation  by  his  hypothesis 
of  "  ontogenetic  grades,''  after  tlic  manner  already 
stated  in  Chapter  II.  Indeed,  it  is  evident  that  in 
no  other  way  can  these  phenomena  be  brought 
within  the  range  of  his  theory.  But  from  this  it 
follows  that  not  only  in  the  case  of  organisms  which 
are  capable  of  somatic  reproduction  is  the  formative 
nucleo^^lasm  (idio-plasm-B)  diffused  throughout  the 
somatic-tissues :  on  the  contrary,  it  must  be  univer- 
sally diffused  throughout  all  the  somatic-cells  of  all 
living^ganisms ;  and  whether  as  it  there  occurs  it  is 
capable  of  reproducing  entire  organisms,  single  organs, 

plants;  but  it  is  ccriainly  much  {greater  than  Wcismaiiii  supposes. 
"  llow  is  it  that  all  j)lanls  cannot  he  ninocUiccd  in  this  way?''  he  a-.ks, 
and  then  ailds,— "  No  one  has  ever  ^rown  a  Itie  from  the  leaf  of  a  lime 
or  an  oak,  or  a  llowerinj^  jilant  In  \\\  a  leaf  of  tlie  tulip  or  the 
convolvulus."  lUit  I  am  told  hy  l)(Jt.uii.-.ts  llial  the  oidy  reason  wiiy 
the  phenomenon  thus  ajipears  to  he  a  rare  one,  is  heeause  it  is  not 
worth  anyhody's  while  to  ^'row  plants  in  this  way  at  a  necessarily 
unsuitahle  season  of  the  year.  Thus,  the  Rev.  (ieorge  llenslow 
writes  me; — "'I'lie  fact  is  that  a)iy  plant  will  reproduce  itself  hy  its 
leaves,  provided  tliat  the  cells  lie  'embryonic,'  ('i.e.,  the  leaf  not 
tooTiear  its  complete  development,  and  that  it  he  not  too  thin, 
so  as  to  provide  enough  nulument  lor  the  hud  t(j  lurni  tdl  il  iiai 
roots." 


Ill 


I 


A- 


54      An  Examination  of  Weismannism. 

single  tissues,  or  a  mere  cicatrix,  depends  only  on 
the  '•  ontogenetic  grade "  of  differentiation  which 
this  diffused  nucleo-plasin  has  (or  has  not)  previously 
undergone.  Moreover,  as  we  have  already  seen,  at 
whatever  ontogenetic  grade  of  differentiation  it  may 
be  present  in  a  given  somatic-tissue,  it  must  there  be 
capable  of  indefinite  self-multiplication.  Therefore, 
in  all  these  resi)ects  this  "formative  nucleo-plasm ''  (or 
idio-|ilasm-B)  of  Weismann  precisely  resembles  the 
''  formative  material"  (or  gemmules)  of  Darwin. 

Lastly,  as  De  Vries  has  pointed  out^,  there  rnust 
beat  least  as  many  divisions  and  subdivisions  in 
the  substance  of  germ-plasm,  as  there  are  differences 
between  the  somatic  organs,  tissues,  and  even  cells, 
to  which  germ-plasm  eventually  gives  rise — no  matter 
through  how  many  ontogenetic  grades  of  idio-plasm 
it  may  first  have  to  pass.  Or,  in  other  words,  we  must 
accept,  as  the  material  basis  of  heredity,  ultimate 
particles  -  of  germ-plasm,  which  are  already  differen- 
tiated into  as  many  diverse  categories  as  there  are 
differences  between  all  the  constituent  parts  of  the 
resulting  soma;  for.  as  shown  in  the  Appendix,  no 
change  in  the  facts  of  the  case  has  been  shown  by 
simply  changing  the  origin.Tl  term  "germ-plasm"  into 
"  idio-plasm."  wherever  the  phenomena  of  ontogeny 
are  concerned.  It  m.iy  be  convenient,  for  the  .sake  of 
presenting  newer  additions  to  the  theory,  to  restrict 
the  tcim  "germ-plasm"  to  'idio-plasm  of  the  first 
ontogenetic  stage";  but  as  idio-plasms  of  all  subse- 

'  Inti (ht'l/itlarc  J'ani^citrsis,  s.  5,5. 

"  I  cmiiloy  the  term  "  ii.ailiclcs,"  instead  of  "  molcciilis,"  licc.iuse 
fillhi)Ut^li  Weismann  nmX  liis  followers  stem  to  prefer  tiie  Inller  term, 
I  can  scnicely  ini:i},nnc  that  tlicy  intend  to  use  it  in  its  oriijinnl,  or 
cliemiial,  sen^e. 


I' 


IVetsmanns  thcoiy  of  Heredity  (1891).  55 

quent  ontogenetic  stages  are  supposed  to  be  ultimately 
derived  from  this  idio-plasm  of  the  first  stage,  it  is 
evident  that  the  particulate  differences  in  question 
must  already  have  been  present  in  the  so-called 
"  undifferentiated  idio-plasm  of  the  first  ontogenetic 
stage."  Unless  we  are  to  have  a  mere  juufirliner  with 
words,  we  cannot  put  into  our  successive  idio-plasms 
any  particles  o.  cinds  difTeriiig  from  those  which  are 
contained  in  the  original  germ-plasm.  Therefore  I 
say  that,  notwithstanding  this  change  of  terminology. 
Weismann  must  continue  to  assume,  as  the  material 
basis  of  heredity,  ultimate  particles  of  germ-plasm 
which  are  already  differentiated  into  as  many  diverse 
categories  as  there  are  difTerences  between  the  parts 
of  the  resulting  soma — although,  of  course,  these 
ultimate  particles  need  not  be  nearly  so  numerous  in 
each  of  tJu'ir  categories  as  they  afterwards  become  by 
self-multiplication  while  forming  each  of  the  resulting 
tissues. 

But  this  is  precisely  what  the  theory  of  pangenesis 
supposes ;  so  that  I  see  no  reason  why  these  ultimate 
particles  of  germ-plasm  should  not  be  regarded  as 
■'gemmules,"  so  far  as  their  size.  niDnber.  tV^.d  function 
are  concerned.  In  point  of  fact,  they  differ  from 
gemmules  only  in  respect  to  their  origTn  :  they  are 
not  particles  derived  from  somatic-cells  of  the  preceding 
generation,  but  particles  derived  from  germ-plasm  of 
the  preceding  generation.  Or,  to  state  the  difference 
in  another  form,  if  vve  regard  the  sexual  elements  as 
constituting  the  physiological  centre  of  the  organism, 
then  the  tTieory  of  germ-plasm  supposes  these  ultimate 
carriers  oFTieredity  to  originate  at  this  centre,  and 
then  to  travel  rtntrifugally  ;  wliilc  the  theor\'  of  pan- 


h: 


iiii 


I 


lifi 


56      All  Exaniinatim  of  Weismannis7n. 

genesis  supposes  them  to  oriiijinate  at  the  periphery, 
and  then  to  travel  centripetal ly. 

This  point  of  difference,  however,  arises  from  the 
deeper  ones,  which — havint^  now  exhausted  the  points 
of  aL^rcement  —  we  must  next  proceed  to  state. 

If,  as  we  have  seen,  -'formative  material"  and 
"germ-plasm"  ^'^rce  in  being  particulate:  in  consti- 
tuting the  material  basis  of  heredity;  in  being  mainly 
lodged  in  highly  .specialized,  or  germinal,  cells  ;  in 
being  nevertheless  also  distributed  throughout  Vie 
general  cellular  tissues,  where  they  are  alike  concerned 
in  all  processes  of  regeneration,  repair,  and  a-sexual 
reproduction  ;  in  having  an  enormously  complex 
■(vvwf*  ^lll^Sl!:'''^''  ^°  ^'^^^  every  constituent  part  of  the  future 

organism  is  already  represented  in  them  by  corre- 
sponding particles ;  in  being  everywhere  ca})ab]e  of  a 
virtually  unlimited  multiplicaiion,  without  ever  losijjg 
their  hereditary  endowments  ;  in  often  carrying  these 
endowments  in  a  dormant  state  through  a  number  of 
generations,  until  at  last  tl:cy  re-appear  again  in  what 
we  recognize  as  reversions  to  ancestral  characters; — 
if  in  all  these  most  important  respects  the  two  sub- 
stances are  supposed  to  be  alike,  it  may  well  appear 
at  first  sight  that  there  is  not  much  room  left  for 
any  difference  between  them.  And.  in  point  of  fact, 
the  onlydiffgxcnce  that  does  obtain  between  them 
admits  of  being  stated  in  two  words, — Continuity, 
and  Stability.  Nevertheless,  although  thi.s  so  few  in 
number,  these  two  points  of  difference  are  points  of 
great  importance,  as  I  wil'  now  proceed  briefly  to 
show. 

If  the  substance  which  constitutes  the  material 
basis  of  heredity  has  been  perpetually  continuous,  in 


Weisinaniis  theory  of  Heredity  (1891).  57 

the  sense  ofncver  havini^  had  any  of  its  hereditary 
endowments  in  any  \va)'  affected  by_£h.C-iIcneral  body- 
tissues  in  which  it^ resides,  the  followin^j  important 
consequences,  it  will  be  remembered,  arise.  The 
process  of  organic  evolution  must  have  been  exclusively 
due  to  a  natural  selection  of  favourable  variations 
occurring  within  the  limits  of  this  substance  itself; 
and  therefore  the  so-called  Larnarckian  factors  can 
never  have  played  any  part  at  au  m  the  evolution  of 
any  but  the  unicelhilar  organisms.  On  the  other  hand, 
if  this  substance  has  not  been  thiis  perpetually  con- 
tinuous, but  more  ox  less  formed  anew  at  each  ontogeny 
by  the  general  body-tissues  in  which  it  resides,  natural 
selection  has  probably  been  in  some  corresponding 
degree  assisted  in  its  work  of  organic  evolution  by  the 
Larnarckian  factors,  with  the  result  that  the  experi- 
ences of  parents  count  for  something  in  the  congenital 
endowments  of  their  offspring.  So  much  for  the 
first  of  the  two  differences  between  germ-plasm  and 
gemmules,  or  the  difference  which  arises  from  the 
perpetual  continuity  of  germ-plasm. 

Touching  the  second  difference,  or  that  which  arises 
from  the  absolute  stability  of  germ-plasm,  it  will  be 
remembered  how  from  this  character  there  arises 
another  important  chain  of  consequences.  Namely, 
individual  variations  of  the  congenital  kind  can  only 
be~"3ue"to  admixtures  of  different  masses  of  germ- 
pTasm  in  every  act  of  .sexual  fertilization ;  natural 
.scTectTon  is  therefore  dependent,  for  the  possibility 
of  its  working,  upon  the  sexual  methods  of  propa- 
gation ;  hence,  natural  selectidu  is  without  any  juris- 
diction among  the  unicellular  organisms,  where  the 
Larnarckian  factors  hold  exclusive  swa\'  :  and  hence, 


il 


!!!i 


mw 


1  :\ 


58      An  Examination  of  Weisniannism. 

also,  the  multicellular  organisms  are  ultimately  depen- 
dent upon  this  absolute  stability  of  their  germ-plasm 
for  all  the  progress  which  they  have  made  in  the 
past,  as  well  as  for  any  progress  which  they  may  be 
destined  to  make  in  the  future. 

Thus  we  see  that  the  two  points  of  difference 
between  gfrm-plasm  and  gem  mules  are  not  merely 
of  great  importance  as  regards  the  particular  problem 
^vhich  is  presented  by  the  phenomena  of  heredity : 
they  are  of  still  greater  importance  as  regards 
the  general  theor\'  of  evolution.  For  if  these  two 
qualities  of  perpetual  continuity  and  absolute  sta- 
bility can  be  proved  to  belong  to  the  material  basis 
of  heredity,  the  entire  theory  of  evolution  will  have 
to  be  reconstructed  from  its  very  foundation — and 
this  quite  apart  from  the  more  special  question  as 
to  the  transmission  of  acquired  characters.  There- 
fore we  shall  presently  have  to  consider  these  two 
alleged  qualities  with  the  care  that  they  demand,  as 
having  been  seriously  suggested  by  so  eminent  a 
naturalist  as  Professor  Weismann.  But,  before  pro- 
ceeding to  do  so,  I  must  briefly  compare  his  theory 
with  that  of  Mr.  Galton. 

"Stirp"  resembles  both  "germ-plasm"  and  "gem- 
mules  "  in  all  the  respects  which  have  above  been 
named  as  common  to  the  two  latter.  ]^ut  it  differs 
fro:i  genunules  and  further  resembles  germ-plasm 
in  all  the  following  particulars.  It  is  derived  from 
the  stirp  of  proceeding  generations,  and  constitutes 
the  sole  basis  of  heredity.  Only  a  part  of  it.  however, 
is  consumed  in  each  ontogeny—  the  residue  being 
handed  over  to  "contribute  to  form  the  stirps  of 
the  offspring."  where  it  undergoes  self-multiplication 


\  i 


n 


Weis7?iajtns  tJieoiy  of  Heredity  (1891).  59 


at  the  expense  of  the  nutriment  supplied  to  it  from 
the  somatic  system  of  the  offspring,  and  so  on  through 
successive  generations  Again,  stirp  is  concerned  in 
all  processes  of  regeneration  and  repair,  in  the  same 
centrifugal  manner  as  germ-plasm  is  so  concerned. 
Furthermore,  the  influence  of  sexual  proi)agation 
in  the  blending  of  hereditary  qualities  of  the  stirp 
is  recognized,  while  the  principle  of  panmixia,  or  the 
cessation  of  selection,  is  entertained,  and  shown  to 
invalidate  the  evidence  of  pangenesis  which  Darwin 
derived  from  the  apparently  transmitted  effects  of 
use  and  disuse  in  our  domesticated  animals  ^  Lastly, 
it  is  clearly  stated  that  on  the  basis  supplied  by 
this  "theory  of  heredity,"  it  becomes  logically  pos- 
sible  to_  dispense  with  the  Lamarckian  principles 
///  toto^  leaving-  natural  selection  as  the  sole  known 
cause  of^rganic  evolution  through  a  perpetual  con- 
tinuity of  stirp,  together  with  individual  variations  of 
the  same,  whether  b\'  sexual  admixture  or  otherwise. 
So  far,  then,  there  is  not  merely  resemblance,  but 
virtual  identity,  between  the  theories  of  stirp  and 
germ-plasm.  Disregarding  certain  speculative  details, 
the  coincidence  is  as  complete  as  that  between 
a  die  and  its  impress.  Rut  although  the  two 
theories  are  thus  similar  in  logical  coustniction,  they 
differ  in  their  interpretati(Mis  of  biological  fact.  That 
is  to  say.  although  Galton  anticii)ated  by  some  ten 
years  all  the  main  features  of  Wcismann's  theory  of 
heredity'-,  and  showed  that,  as  a  matter  of  form,  it  was 

'  Tliis  principle  will  be  considcidl  at  some  leiii^'tli  in  my  next 
volume. 

'•^  Calton  fust  publislu'fl  his  tlicory  in  1S72  Proc.  R.  S..  No.  17,6), 
but  presented  it  in  a  nioio  complete  form  three  years  later  Coiilciiiporary 
Review,  Dec.  1^75,  nnd  /oiinil.  Avtliropol.  Ins/.,  1S75I. 


II 


il'ii 


I 


60      An  Examination  of  Weismannism. 

logically  intact,  he  refrained  from  concluding  on  this 
account  that  it  must  be  the  true  theory  of  heredity. 
He  argued,  indeed,  that  in  the  main  it  was  probably 
the  true  theory  ;  but  he  guarded  his  presentation  of 
it  by  not  undertaking  to  deny  that  there  might 
still  be  some  degree  of  intercommunication  between 
the  material  basis  of  heredity  in  stirp,  and  the 
somatic  tissues  of  successive  organisms.  The  con- 
struction of  a  theory  which,  as  a  matter  of  theory, 
could  dispense  with  the  Lamarckian  principles  i?i  toto, 
was  seeri  to  be  a  very  different  thing  from  proving, 
as  a  matter  of  fact,  that  these  princii)les  are  non- 
existent— and  this,  even  though  it  was  seen  that 
a  recognition  of  the  principle  of  panmixia  must  be 
taken  to  have  considerably  attenuated  the  degree  of 
their  operation  as  previously  estimated  by  Darwin  in 
the  theory  of  pangenesis.  In  short,  after  pointing  out 
that  the  doctrine  of  stirp  might  very  well  adopt 
the  position  which  about  a  decade  later  was  adopted 
by  the  doctrine  of  germ- plasm — namely,  that  of 
altogether  supplantiug  the  doctrine  of  gemmules, — 
Galton  allowed  that  this  could  be  done  only  as 
a  matter  of  formal  speculation  ;  and  that,  as  a  matter 
of  real  interpretation  of  the  facts  of  nature,  it  seemed 
more  judicious  to  stop  at  modifying  the  doctrine  of 
gemmules,  by  provisionally  retaining  the  hypothesis 
of  gemmules,  but  assigning  to  their  agency  a  greatly 
subordinate  rule.     Or  to  quote  his  own  words  : — 


The  conclusion  to  be  drawn  from  the  foregoing  arguments  is, 
that  we  might  ahnost  reserve  our  belief  that  the  structural  [i.e., 
"somatic"]  cells  can  react  on  the  sexual  elements  at  all,  and 
we  may  be  confident  that  at  the  most  they  do  so  in  a  very  faint 
degree ;  in  other  words,  that  acquired  modifications  are  barely, 


w 


IVeisiuamis  t/icory  of  Heredity  (1891).  61 

if  at  .ill,  inherited,  in  the  correct  sense  of  that  word.  If  they 
were  not  herital:)le,  then  tlie  second  t^roiip  of  cases  |i.e.,  those  of 
acquired  as  distingiiislied  from  con;4enital  characters]  would 
vanish,  and  we  should  he  absolved  from  all  further  trouljle ; 
if  they  exist,  in  however  faint  a  degree,  a  complete  theory  of 
heredity  must  account  for  them.  I  propose,  as  already  stated, 
to  accept  the  supposition  of  their  being  faintly  heritable,  and  to 
account  for  them  by  a  modification  of  I'cmgenesis '. 

Seeing,  then,  that  Galton  did  not  undertake  to 
deny  a  possibly  slight  influence  of  somatic-tissues 
on  the  hereditary  qualities  of  stirp,  it  follows  that 
he  did  not  have  to  proceed  to  those  drastic  modi- 
fications of  the  general  theory  of  descent  which 
Wcismann  has  attempted.  Stirp,  like  germ-plasm, 
is  continuous ;  but,  unlike  germ-plasm,  it  is  not 
necessarily  or  absolutely  so.  Again,  stirp,  like  germ- 
plasm,  is  stable;  yet,  unlike  germ-plasm,  it  is  not 
perpetually  or  unalterably  so.  Hence  we  hear  nothing 
from  Galton  about  our  having  to  explain  the  un- 
likcness  of  our  children  to  ourselves  by  variations 
in  our  protozoan  ancestors  ;  nor  do  we  meet  with 
any  of  those  other  immense  reaches  of  deductive 
speculation  which,  in  my  opinion,  merely  disfigure 
the  republication  of  stirp  under  the  name  of  germ- 
plasm. 

Now,  I  allude  to  these,  the  only  important  points  of 
difference  bi'tween  stirp  and  germ-plasm,  for  the 
sake  of  drawing  prominent  attention  to  the  fact  that  it 
makes  a  literally  immeasurable  difference  whether  we 
suppose  the  material  basis  of  heredity  to  be  per- 
petually continuous  and  unalterably  stable,  or  whether 
we  suppose  that  it  is  but  largely  continuous  and  higJily 


( 


'  Journ.  Anthropol,  Inst.  1S75,  p.  7,46. 


1 


r 


f' 


62       An  Exinniuatioti  of  Wcisniauui^ui. 

stiiblc.  In  the  former  case,  all  the  far-reaching 
d'^duction.s  which  Weisniann  draws  with  reference  to 
the  general  theory  of  descent — or  apart  from  the 
more  special  problem  of  heredity — follow  by  way 
of  logical  consequence.  In  the  latter  case,  there  is 
no  justification  for  any  such  deductions.  For,  no 
matter  how  faintly  or  how  fitfully  the  hereditary 
(jualitics  of  Lhe  material  in  cjuestion  may  be  modified 
by  the  somatic-tissues  in  which  it  resides,  or  by 
the  external  conditions  of  life  to  which  it  is  exposed, 
these  disturbances  of  its  absolute  stability,  and  these 
interru[)tions  of  its  perpetual  continuity,  must  cause 
more  or  less  frequent  changes  on  the  part  of  its 
hereditary  qualities — with  the  result  that  specific  or 
other  modifications  of  organic  types  need  not  have 
been  solely  due  to  the  varying  admixture  of  such 
material  in  sexual  unions  on  the  f)ne  hand,  or  to  the 
unassisted  power  of  natural  selection  on  the  other. 
Numberless  additional  causes  of  individual  variation 
are  admitted,  while  the  Lamarckian  princii)les  arc; 
still  allowed  some  degree  of  play.  And  although 
this  is  a  lower  degree  than  Darwin  supposed,  their 
influence  in  determining  the  course  of  organic  evolu- 
tion may  still  have  been  enormous  ;  seeing  that  their 
action,  in  whatever  measure  it  may  be  supposed 
to  obtain,  must  al\va}'s  have  been  cuiimlativc  on  the 
one  hand,  and  dircciiiw  of  variations  in  adaptive 
lines  on  the  other.  Or,  as  Galton  himself  observes, 
in  the  passage  already  quoted,  '•  if  they  exist,  in  Junv- 
evcr  faint  a  degree,  a  complete  theory  of  heredity 
must  account  for  them."  He  saw,  indeed,  that  a  most 
inviting  logic ai  system  could  be  framed  by  denying 
that    they    can    ever    exist     in    any    degree — or,   in 


Weisiiianjis  ikcory  of  llcndi/y  (1891).  63 

other  words,  by  supposing  that  stirp  was  cxiictly 
the  same  as  what  was  afterwards  called  gerni-i)lasni, 
in  that  it  always  occupied  a  separate  '"sphere"'  of 
its  own,  where  its  continuity  has  been  uninterrupted 
"since  the  first  origin  o  life."  liut  Galton  was  not 
seduced  by  the  temptation  to  construct  an  ideally 
logical  system  ;  and  he  had  what  I  regard  as  the 
sound  judgement  to  abstain  from  carrying  his  theory 
of  stirp  into  any  such  transcendental  "si)hcre'"  as  that 
which  is  occupied  by  Weismanns  theory  of  germ- 
plasm,  in  relation  to  the  general  doctrine  of  descent. 

There  is,  then,  a  vast  distinction  between  any 
theory  of  heredity  which  postulates  the  material  of 
heredity  as  highly  stable  and  largely  continuous,  and 
VVeismann's  theory,  which  postulates  this  material  as 
absolutely  stable  and  perpetually  continuous.  But 
we  must  next  take  notice  that  Weismann  himself  has 
not  kept  this  distinction  in  view  with  the  constancy 
which  we  should  have  expected  from  so  forcible 
a  thinker.  On  the  contrary,  although  in  the  con- 
struction of  his  theory  of  evolution  he  never  fails 
to  press  the  postulates  of  absoltitc  stability  and  per- 
petual continuity  to  their  logical  conclusions  in  the 
various  doctrines  above  enumerated  (pp.  .'>7-o<S),  when 
engaged  on  his  more  special  theory  of  heredity  he 
every  now  and  then  appears  to  lose  sight  of  the 
distinction.  Indeed,  he  occasionally  makes  such  large 
concessions  with  regard  to  both  these  postulates, 
that,  were  they  to  be  entertained,  the  occupation  of 
his  critics  would  be  gone  :  his  theory  of  heredity 
would  become  converted  into  Galton's,  while  his 
theory  of  evolution   would  vanish  altogether.     It  is 


r  ^ 


'f!     i 


'I 


64       ^'Ifi  Jixanii nation  oj   [Vcisniamitsni. 


thcrcTnic  necessary  to  quote  some  of  these  con- 
cessions, if  only  to  justify  ourselves  in  subseijuently 
if^norinfj  them.  I  will  i,nve  one  instance  of  each  ; 
but  it  is  necessary  to  preface  the  illustrations  with 
a  few  words  to  mark  emphatically  three  very 
distinct  cases  of  coiiijcnital  variation — leavini,^  aside 
for  tlic  present  tlie  question  whether  or  not  they  all 
occur  in  fact,  as  they  are  held  to  do  by  one  or  other 
of  the  theories  of  heredity. 

1.  The  case  where  impoverished  nutrition  of  the 
body  has  the  effect  of  simply  starving  its  germinal 
material.  This  is  not  a  case  where  either  the  continuity 
or  the  stability  of  such  material  is  affected.  Its  full 
efficiency  as  "  formative  material "  may  indeed  be 
thus  deteriorated  to  any  extent,  so  that  the  proircny 
may  be  to  any  extent  puny  or  malformed  ;  but  this 
will  not  necessarily  cause  any  such  re-shufflint^  of  its 
"molecules"  .ts  will  thereafter  result  in  a  permanent 
phylocjenctic  chan<^e.  At  most  it  will  affect  only  the 
immediate  offsprinij  of  jjoorly  nourished  parents  ;  and 
natural  selection  will  always  be  ready  to  eliminate 
such  inefficient  individuals.  This  case  I  will  always 
hereat '    r  call  the  case  of  nutritive  congenital  chanties. 

2.  The  case  where  germinal  material  is  influenced 
by  causes  which  do  effect  a  re-shuflling  of  its  '•  mole- 
cules," so  that  a  permanent  phylogenetic  change 
docs  result.  Observe,  in  this  case,  it  does  not  signify 
whether  the  causes  arise  from  external  conditic^ns  of 
life,  from  any  action  of  the  soma  on  its  own  germinal 
material,  or  from  so-called  "  spontaneous "  changes 
on  the  part  of  such  material  itself  But  the  one 
cause  which  has  not  been  concerned  in  producing  an 
hcreditaiy  modification   of  this  class  is  the  mixture 


Wcisnianns  theory  of  Ihrcdity  (1891).   65 


Mfl 


of  "fjerm-plasfiis"  in  an  act  of  sexual  union.  In 
hereafter  spcakini;  of  til  is  case  I  will  follow  Weismann's 
terminology,  and  call  coni^cnital  cluui'^cs  thus  produced 
specialized  coiij.^eiiital  chanj^cs. 

3.  Lastly,  we  have  the  case  of  the  Lamarckian 
factors.  This  precisely  resembles  case  3,  save  that 
the  congenital  changes  produced  are  still  more 
"specialized."  For  while  in  the  preceding  case 
the  re-shuflling  before  mentioned  may  have  [)roduced 
a  congenital  change  of  any  kind,  in  the  [Mescnt  case 
the  congenital  change  produced  must  be  of  one 
particular  kind — viz.,  a  reproduction  by  heredity  of 
the  very  same  modification  which  occurred  in  the 
parents.  "The  fathers  have  eaten  sour  grapes,  and 
the  children's  teeth  are  set  on  edge."  This  would  be 
an  extreme  example  of  "  use-inheritance,"  and  so  of 
case  3.  But  if  the  fathers  had  eaten  sour  grapes, 
and  the  children,  instead  of  having  their  teeth  set 
on  edge,  were  to  be  born  with  a  wryneck  or  a  scjuint, 
then  wc  should  have  a  good  example  of  case  2.  In 
order,  then,  to  mark  the  important  distinction  between 
these  two  cases,  I  will  hereafter  call  ^he  highly 
specialized  changes  due  to  the  Lamarckian  factors — 
supposing  such  chan^^cs  to  be  possible — representative 
congenital  changes. 

These  several  distinctions  being  understood,  I  will 
proceed  to  furnish  the  two  quotations  from  Wcismann, 
which  arc  respective'/  illustrative  of  his  concessions 
touching  his  two  fundamental  postulates,  as  previously 
explained. 

We  may  fairly  attribute  to  the  adult  organism  influences 
which  determine  the  phyletic  development  of  its  descendants. 
For  the  germ-cells  arfe   contained  in  the  organism,  and  the 

F 


if   .1 


66       An  Exaininaiion  of  Weismaiinisrn. 

external  influences  which  affect  them  are  intimately  connected 
with  the  state  of  the  organism  in  which  they  he  hid.  If  it  be 
well  nourished,  the  germ-cells  will  have  abundant  nutriment ; 
and,  conversely,  if  it  be  weak  and  sickly,  the  germ-cells  will  be 
arrested  in  their  growth.  It  is  even  possil-'le  that  the  effc  cts  of 
these  influences  may  be  more  specialized ;  that  is  to  say,  they 
may  act  only  upon  certain  parts  of  the  germ  cells.  But  this  is 
indeed  very  different  from  be'itjving  that  the  changes  of  the 
organism  which  result  from  extcrii.il  stimuli  can  be  transmitted 
to  the  gcrm-ccils,  anrl  will  re-devclop  in  the  next  generation  at 
the  same  time  as  that  at  v>'hich  they  arose  in  the  parent,  and  in 
the  same  part  of  the  organism  ^ 


It  will  be  perceived  that  Weismanti  himself  here 
very  clearly  draws  all  the  distinctions  between  cases 
I,  2,  and  3,  as  above  explained.  Therefore  it 
beconvs  the  more  remarkable  that  he  should  not 
have  perceived  how  radically  inconsistent  it  is  in  him 
thus  to  entertain  as  '"possible"  cont^enital  variations 
belonging  to  the  case  2.  For,  as  we  have  now  so 
fully  seen,  the  t^^icorv  of  germ-plasm  (as  distinguished 
from  that  of  stirp)  cannot  entertain  the  possibility  of 
an  hereditary  and  specialized  change  of  any  kind  as 
thus  produced  by  external  conditions  of  life  :  should 
such  a  possibility  be  entertained,  there  must  obviously 
be  an  end  to  the  absolute  stability  of  germ-plasm, 
and  a  conseciuent  co'l  ipse  of  Weismann's  theory  of 
evolution.  ICither  germ-plasm  is  absolutely  stable, 
or  else  it  is  but  highly  stable.  If  it  is  absolutely 
stable,  individual  variations  of  an  hereditary  kind  can 
occur  only  as  results  of  sexual  admixtures  of  germ- 
plasm,  and  Weismana's  theory  of  evolution  is 
established.  But  if  germ-plasm  is  not  absolutely 
stable  (no  matter  in  how  high  a  degree  it  may  be  so) 

'  Esiays,  6tc.,  2ud  cd.,  p.  105. 


Wcisinanns  theory  of  Heredity  (1891).   67 

hereditary  individual  variations  may  be  produced  by 
other  causes,  and  Wcismaun's  theory  of  cvokition 
collapses.  Therefore,  if  \vc  arc  to  examine  his 
theory  of  evolution^  \vc  can  tlo  so  onl)'  by  iij^noring 
such  a  passage  as  the  one  just  (luotetl,  which  sur- 
renders the  postuhi'  J  of  the  absolitlc  stability  of  germ- 
plasm. 

Again,  if  we  arc  to  examine  Weismann's  theory  of 
heredity,  we  must  similarly  ignore  such  a  passap,-  as 
the  following,  where  he  represents  that  he  is  similarly 
prepared  to  surrender  his  still  more  fundamental 
postulate  of  the  pei-pctual  continuity  of  germ-plasm. 

After  remarking  that  some  of  his  own  experiments 
on  the  climatic  varieties  of  certain  butterflies  raise 
such  difficulties  against  his  whole  theory  of  heredity 
that  even  now  he  '•  cannot  explain  the  facts  otherwise 
than  by  supposing  the  passive  acquisition  of  characters 
produced  by  the  direct  influence  of  climate,"  he  goes 
on  to  remark  more  generally — '  We  cannot  exclude 
the  possibility  of  such  a  transmission  occasionally 
occurring,  for,  even  if  the  greater  part  of  the  effects 
must  be  attributed  to  natural  selection,  there  might 
be  a  smaller  part  in  certiin  cases  which  depends 
on  this  exceptional  factor ^  " — i.e.,  the  Lamarckian 
factor ! 

Now,  it  must  be  particularly  noted  that  in  this 
passage  Weismann  is  speaking,  not  as  in  the  previous 
passage,  of  scpcialized  congenital  characters,  but  of 
representative  congenital  characters.  In  other  words, 
he  here  entertains  the  possibility  which  in  the  passage 
previously  quoted  he  very  properly  rejects — namely, 
"that   changes   of  the   organism   which    result    from 

'  Essays,  ike,  ami  l\1.,  p.  loo. 
F    2 


ii 


i 


6S      An  Examination  of  Weismannism. 

external  stimuli  can  be  trahsmitted  to  the  germ-cells, 
and  will  rc-dcvclop  in  the  next  generation  at  the  same 
time  as  that  at  ivltich  they  arose  in  the  parent,  and  in 
the  same  part  of  the  organism."  But  it  is  evident  that 
if  the  theory  of  germ-plasm  is  undermined  by  the 
concession  made  in  the  passage  thus  previously 
quoted,  in  the  passage  last  quoted  a  match  is  put 
to  the  fuse.  It  does  not  signify  v/hether  the  particular 
case  of  the  butterflies  in  question  will  ever  admit  of 
any  other  explanation  more  in  accordance  with  the 
tlieory  of  germ-plasm  :  the  point  is  that  in  no  case 
can  this  theory  entertain  the  possibility  of  causes 
other  than  admixtures  of  germ-plasm  in  sexual 
unions  producing  hereditary  changes,  (A)  of  any 
kind,  (B)  still  less  of  a  specialized  kind,  and  (C)  least 
of  all  of  a  representative  kind.  For  the  distinguishing 
essence  of  this  theory  is,  that  germ-plasm  must  always 
have  moved,  so  to  speak,  in  a  closed  orbit  of  its  own  : 
its  "  sphere "  must  have  been  perpetually  distinct 
from  those  of  whatever  other  "  plasms "  there  may 
be  in  the  constellations  of  living  things.  So  that,  in 
such  passages  as  those  just  quoted,  Weismann  is  not 
only  destroying  the  very  foundations  of  his  general 
theory  of  evolution,  but  at  the  same  time  he  is 
identifying  his  more  special  theory  of  heredity  with 
those  which  had  been  already  published  by  his 
predecessors,  and  more  particularly  by  Galton. 
Now,  it  is  not  Galton's  theory  that  we  are  con- 
sidering ;  and  therefore  we  must  hereafter  ignore 
those  fundamental  admissions,  whereby  Weismann 
every  now  and  p^ain  appears  ready  to  relincjuish  all 
that  is  most  distinctive  of,  or  original  in,  his  own 
elaborate  system  of  tlieories. 


4    S,a>flEfr- 


Weismanns  theory  of  Heredity  (1891).   69 

It  is,  indeed,  impossible  not  to  admire  the  candour 
of  these  admissions,  or  to  avoid  recognizing  the  truly 
scientific  spirit  which  they  betoken.  But,  at  the  same 
time,  one  is  led  to  doubt  whether  in  making  them 
Professor  Weismann  has  sufficiently  considered  their 
full  import.  He  appears  to  deem  it  of  compnrativcly 
little  importance  whether  or  not  acquired  characters 
can  sometimes  and  in  some  degrees  influence  the 
hereditary  qualities  of  germ-plasm,  provided  he  can 
show  that  much  tJic  .arger  part  of  the  phenomena  of 
heredity  must  be  ascribed  to  the  continuity  of  germ- 
plasm.  In  o^her  words,  he  seems  to  think  that  it 
matters  but  little  whether  in  the  course  of  organic 
evolu^^^ion  the  Lamarckian  factors  have  played  but 
a  very  ^^v'bordinate  part,  or  whether  they  have  not 
played  Dny-  part  at  all.  Moreover,  I  have  heard  one 
or  two  prominent  followers  of  Weismann  give  public 
expression  to  the  same  opinion.  Therefore  I  must 
re[)eat  that  it  makes  a  literally  immeasurable  difference 
whether  we  suppose,  with  Galton,  that  the  Lamarckian 
factors  .may  sometimes  and  in  some  degrees  assert 
themselves,  or  whether  we  suppose;,  with  the  great 
bulk  of  Weismann's  writings  and  in  accordance  with 
the  logical  requirements  of  his  theory,  that  they  can 
never  possibly  occur  in  any  degree.  The  distinctive 
postulate  of  his  theory  of  heredity,  and  one  of  the 
two  fundamental  doctrines  on  which  he  founds  his 
further  theory  of  evolution,  is,  that  the  physiology  of 
sexual  reproduction  cannot  admit  of  any  inversion  of 
the  relations  between  '"germ-plasm  "  and  '"somatic  idio- 
plasm ^"  This  is  a  perfectly  intelligible  postulate,  but 
it  is  not  one  with  which  we  may  play  fast  and  loose. 

'  Set-  lor  L'xampl  ■,  Essays,  \>.  2:.(j. 


li 


I 


I 


1 


70      An  Examination  of  Wcisniannism. 

luthcr  there  is  such  a  physiological  mechanism  as  it 
announces,  in  which  case  the  relations  in  question  can 
never  be  inverted  "occasionally,"  any  more  than  ra£;;s 
may  "occasionally"  help  to  construct  the  mill  which 
is  to  form  them  into  paper  ; — or  else  there  is  no  such 
mechanism,  in  wiiich  case  we  may  have  to  do  with 
c^emmules,  physiological  units,  stirp,  micellae,  pangenes, 
plastidules,  or  any  of  the  other  hypothetical  "  carriers 
of  heredity  "  to  which  our  predilections  may  happen 
to  incline  ;  but  the  one  substance  with  which  we 
certainly  have  not  to  do  is  germ-plasm  ^ 

After  these  tedious  but  necessary  preambles,  we 
may  now  proceed  to  examine  Professor  Weismanns 
postulate  as  to  the  perpetual  continuity  of  germ-plasm, 
with  its  superstructure  in  his  theory  of  heredity — 
reserving  for  the  next  chapter  our  examination  of  his 
further  postulate  touching  the  absolute  stability  of 
germ-plasm,  with  its  superstructure  in  his  theory  of 
evolution. 

The  evidence  which  Weismann  has  presented  in 
favour  of  his  fundamental  postulate  of  the  perpetual 
continuity  of  germ-plasm  may  be  conveniently  dealt 

'  On  previous  nccnsions,  when  inconsistencies  have  been  brought  to 
the  notice'  of  I'roitv^SDr  Weismann  by  his  critics,  he  has  complained  that 
sufficient  allowance  was  not  made  for  the  fact  of  his  having  published 
his  sundry  essays  at  different  times.  This,  of  course,  is  a  satisfactory 
answer  in  cases  where  criticism  refers  to  a  growing  theory,  the  later 
additions  to  which  supersede  certain  parts  of  the  earlier  construction. 
But  clearly  the  answer  is  not  avnilaltle  in  cases  where  one  set  of 
statements,  touching  fundamental  iirincijiles  of  tlie  theory,  are  directly 
opjiosed  to  otliers.  A  logical  contradiction  is  not  affected  by  dates 
of  jndilication,  and  where  the  contradictory  statements  have  reference 
to  the  vital  essence  of  a  theory,  it  is  njunily  impossiMe  for  the  theory 
to  ci)nipiise  tiiem  whether  they  be  presented  simultanei)usly  or  suc- 
cessively. 


!1 


IJS*- 


Weisuumns  theory  of  H end  if y  (1891).   71 

with  under  two  heads  — namely,  indirect  evidence  as 
derived  from  general  reasoning,  and  direct  evidence 
derived  from  particular  facts. 

The  general  reasoning  is  directed  to  show,  (1)  that 
there  is  no  evidence  of  the  transmission  of  acquired 
characters  ;  (2)  that  the  theory  of  pangenesis  is 
"inconceivable":  and.  (3)  that  the  alternative  theory 
of  germ-plasm  is  amply  conceivable.  Now,  to  the 
best  of  my  judgement,  not  one  of  these  propositions  is 
borne  out  by  the  general  reasoning  in  question.  Ikit 
as  the  latter  is  almost  entirely  of  an  a  prion  character, 
and  also  of  a  somewhat  abstruse  construction,  I  think 
the  patience  of  any  ordinary  reader  will  be  saved  by 
relegating  this  part  of  our  subject  to  an  Appendix. 
Therefore,  remarking  only  that  any  one  who  cares  to 
look  at  Appendix  I  ought,  in  my  ojjinion,  to  perceive 
that  there  is  no  real  evidence  against  the  iransmission 
of  acquired  characters  to  be  derived  from  Weismann's 
cjeneral  reasonini:^  in  this  connexion,  I  will  at  once 
proceed  to  consider  the  evidence  which  he  has 
adduced  in  the  way  of  particular  facts. 


In  the  first  place,  as  one  result  of  his  brilliant 
researches  on  the  llydrouicdiisac,  he  has  found  that 
the  generative  cells  occur  only  in  certain  locali/.ed 
situations,  which,  however,  vary  greatly  in  different 
species,  though  they  are  always  constant  for  the  same 
species.  lie  has  also  found  that  the  varying  situations 
in  different  species  of  the  localized  or  generative  areas 
correspond,  place  for  place,  with  successive  stages  in 
a  process  of  gradual  transposition  which  has  occurred 
in  the  phylogenx'  of  the  Ilydroineditsac.  Lastly,  he 
has    found    that    in    each    ontogeny  these  successive 


■|f.  m^ 


W' 


72      An  Exammation  of  Weisrnarinhm. 

stages  of  transposition  are  repeated,  with  the  result 
that  during  the  individual  lifetime  of  one  of  these 
animals  the  germ-celh'  migrate  through  the  body,  from 
what  used  to  be  their  ancestral  situation  to  what  's 
now  the  normal  situation  for  that  particular  speciei.. 
Such  being  the  facts,  Weismann  argues  from  them 
that  the  germ-cells  of  the  llydrovieditsae  are  thus 
proved  to  present  properties  of  a  peculiar  kind,  which 
cannot  be  supplied  by  any  of  the  other  cells  of  the 
organism  ;  for,  if  they  could,  whence  the  necessity  for 
this  migration  of  these  particular  cells?  Of  course 
it  follows  that  these  peculiar  properties  must  depend 
on  the  presence  of  some  peculiar  substance,  and  that 
this  is  none  other  than  the  "  germ-plasm,"  which  here 
exhibits  a  demonstrable  "continuity"  throughout  the 
entire  phylogeny  of  these  unquestionably  very  ancient 
Metazoa. 

The  second  line  of  direct  evidence  in  favour  of  the 
continuity  of  germ-plasm  which  Weismann  has  ad- 
duced is,  that  in  the  case  of  some  invertcbrated  animals 
t!>e  sexual  apparatus  is  demonstrably  separated  as 
reproductive  cells  (or  cells  which  afterwards  give  rise 
to  the  reproductive  glands)  at  a  very  early  period  of 
ontogeny — so  early  indeed,  in  certain  cases,  that  this 
separation  constitutes  actually  the  first  stage  in  the 
process  of  ontogeny.  Therefore,  it  is  argued,  we  may 
regard  it  as  antecedently  improbable  that  the  after-life 
of  the  individual  can  in  any  way  affect  the  congenital 
endowments  of  its  ova,  seeing  that  the  ova  have  been 
thus  from  the  first  anatomically  isolated  from  all  the 
other  tissues  of  the  organism. 

The  third  and  only  cither  line  of  direct  evidence  is, 
that  organisms  which  ha\e  been  produced  partheno- 


Weis7nanns  theory  of  Heredity  (189 1).  73 

genetically,  or  without  admixture  of  germ-plasms  in 
any  previous  act  of  sexual  fertilization,  do  not  exhibit 
conejenital  variations. 

Taking,  then,  these  three  lines  of  verification  separ- 
ately, none  of  them  need  detain  us  long.  For  although 
the  fact  of  the  migration  of  germ-cells  becomes  one  ot 
great  interest  in  relation  to  Wcismann's  theory  after 
the  tJieory  has  been  accepted^  the  fact  in  itself  docs  not 
furnish  any  evidence  in  support  of  the  theory.  In 
the  first  place,  it  tends  equally  well  to  support  Galton's 
theory  of  stirp ;  and  therefore  does  not  lend  any 
special  countenance  to  the  theory  of  germ-plasm — or 
the  theory  that  there  cannot  now  be,  and  never  can 
have  been,  any  communication  at  all  between  the 
plasm  of  the  germ  and  that  of  the  soma.  In  the 
second  place,  the  fact  of  such  migration  is  not  incom- 
patible even  with  the  theory  of  pangenesis,  or  the 
theory  which  supposes  such  a  communication  to  be 
extremely  intimate.  There  may  be  many  other 
reasons  for  this  migration  of  germ-cells  besides  the 
one  which  Weisrnann's  theory  supposes.  For  example, 
the  principle  of  physiological  economy  may  very 
well  have  determined  that  it  is  better  to  continue  for 
reproductive  purposes  the  use  of  cells  which  have 
already  been  specialized  t  nd  set  apart  for  the  execu- 
tion of  those  purposes,  tban  to  discard  these  cells 
and  transform  others  into  a  kind  fitted  to  replace 
them.  Even  the  theory  of  pangenesis  requires  to 
assume  a  very  high  tlcgree  of  specialization  on  the 
part  of  germ -cells  ;  and  as  it  is  the  fact  of  such 
specialization  alone  which  is  proved  by  VVeismann's 
observations.  I  do  not  see  that  it  constitutes  any 
criterion  between  his  theory  of  heredity  and  that  of 


74       -^^^  Exa7nination  of  Weisinannism. 

Darwin — still  less,  of  course,  between  his  theory  and 
that  of  Galton.  Lastly,  in  this  connexion  we  ought 
to  remember  that  the  Ilydyomcditsae  are  organ- 
isms in  which  the  specialization  in  question  happens 
to  be  least,  as  is  shown  by  the  fact  that  entire  indi- 
viduals admit  of  being  reproduced  from  fragments  ot 
somatic-tissues ;  so  that  these  are  organisms  where 
we  would  least  ex[)cct  to  meet  with  the  migration 
of  germ-cells,  were  the  purpose  of  such  migration 
that  which  Weismann  suggests.  This  line  of  evidence 
therefore  seems  valueless. 

Nor  does  it  appear  to  me  that  the  second  line  of 
evidence  is  of  any  more  value.  In  the  first  place, 
there  is  no  shadow  of  a  reason  for  supposing  that  an 
apparently  anatomical  isolation  of  germ-cells  neces- 
sarily entails  a  physiological  isolati.Qn  as  regards 
their  special  function— all  "physiological  analogy," 
indeed,  being  opposed  to  such  a  view,  as  is  shown 
in  Appendix  I.  In  the  second  place,  there^js  no 
proof  of  any  anatomical  isolation,  as  we  may  like- 
wise see  in  that  Appendix.  In  the  tlijrd  place,  the 
fact  relied  upon  to  indicate  such  an  isolation — viz., 
the  early  formation  of  germ-cells  — is  not  a  fact  of  any 
general  occurrence.  On  the  contrar}',  it  obtains  only 
in  a  comparatively  small  number  of  animals,  while  it 
does  not  obtain  in  any  plants.  In  the  Vertebrates, 
for  example,  the  reproductive  cells  are  not  dif- 
ferentiated from  the  somatic  cells  till  after  the  em- 
bryo has  been  fully  formed;  while  in  plants  their 
development  constitutes  the  very  last  stage  of  onto- 
geny. In  the  fourth  place,  the  argument,  even  for 
what  it  is  worth,  is  purely  deductive  ;  and  deductive 
reasoning  in  such  a  case  as  this — where  the  phonemena 


m 


•i 


IVcisnianiis  theory  of  Heredity  (1891).  75 

are  enormously  complex  and  our  I'f^norancc  unusually 
profound — is  always  precarious.  Lastly,  in  the  fifth 
place,  Weismann  has  now  himself  abandoned  this 
argument.     For  in  one  of  his  later  essays  he  says  : — 

Those  instances  of  early  separation  of  sexual  from  somatic 
ce'ls,  upon  which  I  have  often  insisted  as  indicatint^  the  con- 
tinuity of  the  gerni-[)lasm,  do  not  now  appear  to  be  of  such 
conckisive  importance  as  at  the  time  when  we  were  not  sure 
about  the  locaUzation  of  the  plasm  in  the  nuclei.  In  the  great 
majority  of  cases  the  germ-cells  are  not  separated  at  the 
beginning  of  embryonic  development,  but  only  in  some  of  the 
..iter  stages.  ...  It  therefore  follows  that  cases  of  early  separa- 
tion of  the  germ-cells  afford  no  proof  of  a  direct  jjersistence  of 
the  parent  germ-cells  in  those  of  the  offspring. 

The  last  line  of  direct  evidence,  or  that  derived 
from  the  alleged  non-variabilily  of  parthenogenetic 
organisms,  is,  as  Professor  Vines  has  shown,  opposed 
to  fact.  Therefore,  in  liis  later  writings,  Weismann 
has  abandoned  this  line  of  evidence  also. 

Upon  the  whole,  then,  we  must  conclude  with  regard 
to  the  fundamental  postulate  of  perpetual  continuity, 
that  there  is  actually  no  evidence  of  a  direct  kind  in 
its  favour.  And,  as  Weismann's  arguments  of  an 
indirect  kind  are  dealt  with  in  Appendix  I,  it  remains 
only  to  state  such  evidence  per  contra  as,  to  the  best 
of  my  judgement,  appears  valid. 

The  fundamental  proposition  which  we  have  been 
considering,  and  to  the  further  consideration  of  which 
we  have  now  to  proceed,  is,  in  effect,  that  germ-plasm 
differs  from  stirp  in  having  hcQU  pcrpet/ia/iy  restricted 
to  a  "  sphere  "  of  its  own.  "  si/icc  tJic  first  origin  of 
life."  Criticism,  therefore,  must  be  directed  to  show 
that  the  "sphere"'  in  ciuestion  has  not  been  proved 


il  : 


3  i 


76      An  Examination  of  Weismannism. 


so  entirely  inclci)cnclent  as  this  fundamental  proposition 
sets  forth ;  but  that,  on  the  contrary,  there  appears 
to  be  a  certain  aiTiDunt  of  reciprocal  action  between 
this  sphere  and  that  of  the  somatic-iissucs  —  even 
though  we  may  ai^ree  (as  I  myself  agree)  with  Galton 
in  holdinc^  that  the  degree  of  such  reciprocal 
action  is  neither  so  intimate  nor  so  constant  as  it 
was  held  to  be  by  Darwin.  This,  indeed,  is  the 
direction  which  the  course  of  our  criticism  has  taken 
already.  For  it  has  just  been  shown  that  Weismann 
has  failed  to  adduce  any  facts  (preceding  text)  or 
considerations  (Appendix  I)  in  support  of  his  fun- 
damental proposition  as  above  stated,  save  such  as 
proceed  on  a  prior  acceptance  of  the  proposition 
itself.  The  facts  and  considerations  which  he  has 
adduced  are  therefore  useless  as  evidence  in  support 
of  this  proposition,  although  they  would  admit  of 
being  explained  by  it  supposing  it  to  have  been 
already  substantiated  by  any  facts  or  c  )nsiderations  of 
an  independent  kind.  Which  is  merely  another  way  of 
saying,  as  already  said,  that  there  is  no  evidence  in 
favour  of  the  proposition. 

But  I  am  now  about  to  argue  that  there  is  evidence 
against  the  proposition.  For  I  am  about  to  argue, 
not  only  as  heretofore  that  for  anything  Weismann  has 
shown  to  the  contrary  there  may  be  a  certain  amount 
of  reciprocal  action  between  the  sphere  of  germinal- 
substance  and  the  sphere  of  body-substance  ;  but  that, 
as  a  matter  of  fact,  there  is  a  certain  amount  of  such 
reciprocal  action. 

Without  laying  undue  stress  on  the  intimate 
"  correlation  "  that  subsists  between  the  reproductive 
organs  and  all  other  parts  of  the  organism,  I  never- 


Weismanns  theory  of  Heredity  (1891).  77 

thcK'ss  think  that  the  fact  ou^ht  here  to  be  noted. 
For  the  chani^cs  which  occur  at  puberty  and  after  the 
reproductive  functions  have  ceased,  as  well  as  those 
wliicir~fYiiiy"  be  artifTcially  produced  by  castration. 
&c.,  prove  at  any  rate  some  extremely  important 
association  between  the  soma  as  a  whole  and  its 
reproductive  apj^aratus  as  a  whole.  No  doubt  it  may 
projjerly  enouL^h  be  answered  that  this  proof  does  not 
extend  to  the  vital  point  of  showing  the  association 
to  be  between  the  soma  as  a  whole,  and  that  i)articular 
part  of  tile  reproductive  apparatus  in  which  the 
"carriers  of  heredity"  reside — niunely,  the  ova  and 
spermatozoa  ;  and,  therefore,  that  the  facts  in  question 
may  be  due  only  to  some  chanj^^ed  conditions  of 
nutrition  on  the  part  of  the  somatic-tissues  which 
these  alterations  on  the  part  of  the  reproductive  Ljlands 
entail.  On  this  account  we  must  fully  allow  that  the 
facts  in  question  are  not  in  themselves  of  any  con- 
clusive weight ;  but  I  think  they  are  worth  mentioning, 
because  they  certainly  seem  to  countenance  the  theory 
which  sup[)ose3  some  reciprocal  influence  as  exercised 
by  the  germinal  elements  on  the  somatic-tissucs_and 
vice  versa,  rather  than  they  do  the  theory  which  sup- 
poses the  germinal  elements  and  the  somatic-tissues 
to  have  always  occupied  totally  different  "  spheres." 

Here,  however,  is  a  stronger  class  of  facts.  It  has 
not  unfrequently  been  observed,  at  any  rate  in  mam- 
mals, that  when  a  female  has  borne  progeny  to 
a  maleof  one  variety,  and  subsequently  bears  progeny 
to  a  male  of  another  variety,  the  younger  progeny 
presents  a  more  or  less  unmistakable  resemblance  to 
the  father  of  the  older  one.  Now.  this  is  a  fact  to 
which  Weismann  has  nowhere  alluded  ;  and  therefore 


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78      An  F.XiVtiination  of  IVcisniaiinism. 


I 

I 
t  I 


I  do  not  know  how  he  would  meet  it.  Hut,  as  far  as 
I  can  sec,  it  can  l)e  explained  only  in  one  or  other  of 
two  ways.  Either  there  must  be  some  action  of_the 
spermatic  element  on  the  hitherto  unripe_ovum^oj;j;lse 
this  element  must  e.xercisc  some  influence  on  the  so- 
matic-tissues of  the  female,  which  in  their  turn  act  uiwn 
the  ovum  \  Now,  I  do  not  deny  that  the  first  of  these 
possibilities  micjlit  be  reconcilable  with  the  hypothesis 
of  an  absolute  continuity  of  ^crm-plasm  ;  for  it  is 
conceivable  that  the  life  of  L^ermplasm  is  not  co- 
terminous with  that  of  the  spermato/oa  which  convey 
it.  and  hence  that,  if  the  carriers  of  heredity,  after  the 
disintei^ration  of  their  containing  si)ermato/.oa,  should 
ever  penetrate  an  unri[)e  ovum,  the  L'erm-j)lasm  thus 
introduced  mi_L!;ht  remain  dormant  in  the  ovum  until  the 
latter  becomes  mature,  and  is  then  fertilized  by  another 
sire.  In  this  way  it  is  conceivable  that  the  hitherto 
dormant  germ-plasm  of  the  previous  uire  might  exercise 
some  inlluence  on  the  progeny  of  a  subse(]uent  one. 
lUit  it  seems  clear  that  the  second  of  the  two  possi- 
bilities above  named  could  not  be  thus  brought  within 
the  hypothesis  of  an  absolute  continuity  of  germ- 
l)lasm.  Therefore  it  seems  that  the  school  of  VVeis- 
mann  muse  adopt  the  first,  to  the  exclusion  of  the 
second.  Unfortunately  for  them,  however,  there  is 
another  (and  clearly  analogous)  fact,  which  goes  to 
exclude  the  first  po.ssibility,  and  most  definitely  to 
substantiate  the  second.  For,  in  the  case  of  plants, 
where  there  can  be  no  second  [)ro-^eny  borne  by  the 


su 


*  The  possil)ility  of  any  s]iciniati>zoa  of  the  first  iinprcQiiatioii 
rviviiij;  to  lake  part  in  the  sfcoml  is  cxchidcd  by  tlie  fact  tiiat  the 
iLii<>iiu'i\(in  occurs  iu  niaiiimals,  ami,  apparently,  may  e.\tuul  over  twc 


or  tlucc  Inters. 


U'cismaiin s  theory  of  Heredity  (1891).   79 

same  "  ovary,"  but  where  \vc  happen  to  be  able  to  see 
that  a.  marked  effect  is  sometimes  produced  on  the 
somatic-tissues  of  the  rnother  by  the  pollen  of  the 
father,  there  can  be  no  question  as  to  the  male  element 
being  able  to  exercise  a  ilircct  influence  on  the  soma 
of  the  female.  Consequently,  whatever  we  may  think 
with  regard  to  the  case  of  animals,  the  facts  with  reL,Nucl 
to  plants  are  in  themselves  enough  to  sustain  the  only 
position  with  which  we  are  concerned  viz.,  that  the 
male  element  is  capable  of  directly  modifying  the 
female  soma. 

The  facts  with  regard  to  plants  are  these.  When 
one  variety  fcrtili/cs  the  ovules  of  another,  not 
unfrequcntly  the  influence  extends  bejond  the  ovules 
to  the  ovarium,  and  even  to  the  calyx  and  flower- 
stalk,  of  the  mother  plant.  This  influence,  which 
may  affect  the  shape,  size,  colour,  and  texture  of  the 
somatic-tissues  of  the  mother,  has  been  observed  in  a 
large  number  of  plants  belonging  to  many  different 
orders.  The  details  of  the  matter  have  ahead)'  been 
dealt  with  by  Darwin,  in  the  eleventh  chai)ter  of  his 
work  on  \  'ariadon,  &c. ;  and  this  is  what  he  says. 
The  italics  are  mine. 


^h 


The  proofs  of  the  action  of  forcifrn  po'len  on  the  mother -plant 
have  been  given  in  considenible  iletail,  l)cc;uise  this  aciiun  is  of 
the  hij^^hest  theoretical  iinporlance,  and  Ijecaiise  it  is  in  itself 
a  remarkable  and  ai)|)arently  anomalous  circumstance.  Thai  it 
if  remarkable  undir  a  |)hysiological  point  of  \  iew  is  clear,  for 
the  male  element  not  only  affects,  in  accordance  with  its  proper 
function,  the  },'erm,  but  at  the  same  time  various  i)arts  of  the 
mother-plant,  in  the  siuiie  maiincr  as  il  itjj\cls  ilic  saiiic  piirts  in 
tlie  seminal  offspriiii:;  from  tlie  siivie  lico  parents.  We  thu!r 
learn  that  an  ovule  is  not  indispensable  for  the  reception  of  tha 
intluence  ol  the  male  element. 


8o      An  Examination  of  Weisniannism, 

Darwin  then  proceeds  to  show  that  this  direct  action 
of  the  male  clement  on  the  somatic  tissues  of  another 
organism  is  not  so  rare  or  anomalous  as  i^^  at  first 
sight  appears ;  for  in  the  case  of  not  a  few  Howers  it 
comes  into  ;)lay  as  a  needful  preliminary  to  fertiliza- 
tion.    Thus,  for  instance  : — 

Cjirtner  j^'radually  increased  the  number  of  pollen  grains 
until  In;  succeeded  in  fertilizing  a  Malva.  and  has  proved  that 
many  grains  arc  first  expended  in  the  development,  or,  as  he 
expresses  it,  in  the  satiation,  of  the  pistil  and  ovarium.  Again, 
when  one  plant  is  fertilized  by  a  widely  distinct  species,  it  often 
happens  that  the  ovarium  is  fully  and  quickly  developed 
without  any  seeds  lieing  formeil  ;  or  the  coats  of  the  seeds  are 
formed  without  any  embryo  being  developed  therein. 

So  mucli,  then,  in  proof  of  the  direct  action  of 
the  male  element  on  the  somatic-tissues  of  another 
organism.  It  remains  to  show  that  a  similar  action 
may  be  exercised  by  this  element  on  the  somatic- 
tissues  of  its  own  organism.  This  has  been  proved  by 
llildebrand,  who  found  "that  in  the  normal  fertiliza- 
tion of  several  Orchideae,  the  action  of  the  plants 
own  pollen  is  necessary  for  the  development  of  the 
ovarium  ;  and  that  this  development  takes  place  not 
only  long  before  the  pollen  tubes  have  reached  the 
ovules,  but  even  before  the  placentae  and  ovules  have 
been  formed  "  ;  so  that  with  these  orchids  the  pollen 
acts  directly  on  their  own  ovaria,  as  a  prelim inary~to 
the  formation  of  the  ovules  which  are  subsequently 
to  be  fertilized. 

It  is  to  be  regretted  that  Professor  Weismann 
has  not  given  us  his  opinion  upon  this  whole  class 
of  facts,  for  assuredly  they  api)ear  directly  to  con- 
tradict his  theory.     The  theory  is,  '•  that  the  germ- 


IVci's/fiaini's  theory  of  Ilcrcdiiy  (1891).    81 

plasm  and  the  somato-plasin  liavc  always  occupied 
different  spheres":  thejact_is,  that  the  j^erin-phisni 
may  directly  act  upon  the  somato-plasm,  both  within 
and  beyond  the  lin^its  of  the  same  ur;.;anism. 


Hitherto  we  have  been  considcrini;  certain  very 
definite  facts,  which  seem  to  prove  that  the  Ljerminal 
elements  are  able  directly  to  affect  the  somatic-tissues. 
VVe  have  next  to  consider  such  facts  as  seem  to  prove 
the  opposite  side  of  a  reciprocal  relationship — viz., 
that  the  somatic-tissues  are  able_directly  to  idfect 
the  germinal  elements. 

And  here  there  are  two  distinct  lines  of  evidence 
to  be  distinguished. 

Firstly,  in  certain  cases — exceptional  it  is  true,  but 
this  does  not  signify— somatic-tissues  have  been  found 
capable  of  modifying  the  hereditary  endowments  of 
germinal  elements  by  means  of  simple  grafting.  This 
Hne  of  evidence  has  also  been  disregarded  both  by 
Weismann  and  his  followers ;  but  it  is  nevertheless  an 
important  one  to  consider.  For,  if  it  be  the  case 
that  the  somatic-tissues  of  an  organism  A,  by  being 
merely  grafted  on  those  of  organism  B.  can  so  affect 
the  germinal  elements  of  B  as  to  cause  their  offspring 
to  i'escmble  A — or,  contrariwise,  if  the  somatic-tissues 
of  A  can  thus  act  on  B  -then,  although  it  may  not 
be  properly  said  that  any  "acquired  cnaracters"  have 
been  transmitted  from  A  to  the  progeii)-  of  B,  (or 
vice  versa,)  such  an  a-sexual  transmission  of  alien 
characters,  in  its  relation  to  the  theory  of  germ-i)hism, 
is  scarcely  less  awkward  than  are  certain  facts  which 
they  appear  to  prove. 

Secondly,  that  acquired  characters  may  be  trans- 

G 


{  1 

u 

1 1 


82      An  Exauiination  of  W^cisnianmsm. 

mittcd  to  prc\cjcny  by  the  more  ordinary  methods  of 
sexual  propa<4'ation(Laniarckian  factors).  This  second 
line  of  evidence  will  be  fully  and  independently  dealt 
with  in  future  chapters,  specially  devoted  to  the 
subject.  Therefore  we  have  here  to  consider  only  the 
first. 

Now,  the  force  of  this  first  line  of  evidence  will 
become  apparent,  if  wc  rcfiect  that  the  only  way 
in  which  the  facts  can  be  met  by  W'eismann's  theory, 
would  be  by  supi)()sin^f  that  the  somatic  germ-plasms 
which  are  respectively  diffused  throu;j[h  the  cellular 
tissues  of  the  scion  and  the  L^raft  become  mixed  in 
some  such  way  as  they  mii^ht  have  been,  had  the 
hybrid  been  due  to  seminal  propagation  instead  of  to 
simple  grafting.  But  against  this,  the  only  interpre- 
tation of  the  facts  wliich  is  open  to  the  theory,  there 
lies  the  follcnving  objection,  which  to  me  appears 
insuperable. 

Where  sexual  cells  are  concerned  there  is  alwa)'s 
a  definite  arrangement  to  secure  penetration  of  the 
one  by  the  other,  and  we  can  see  the  necessity  for 
such  an  arrangement  in  order  to  effect  an  admixture  of 
their  nuclear  contents,  where  alone  germ-plasm  is 
supposed  by  Weismann's  theory  to  reside.  Ikit  in 
tissue-cells  which  have  not  been,  thus  s[)eciali/,ed,  it 
would  be  difficult  to  believe  that  nuclear  contents  can 
admit  of  being  intimately  fiised  by  a  mere  apposition 
of  cell-walls.  For  not  only  are  the  nuclear  contents  of 
any  two  such  cells  thus  separatetl  from  one  another 
by  two  cell-walls  and  two  masses  of  "  cytoplasm  "  ; 
but  it  is  not  enough  to  supi)Ose  that  in  order  to 
produce  a  graft-h\brid  only  two  of  these  .somatic-cells 
need  mix  their  nuclear  contents   as  we  know  is  all 


ays 

the 

for 

of 

is 

in 

it 

an 

lion 

of 


to 

:lls 
ill 


Wcisnuinns  theory  of  lie  natty  (1891).    83 

that  is  required  in  order  to  ])roduce  a  seminal  hybrid 
by  means  of  sexual  cells.  On  the  contrary,  in  the 
former  case  most,  if  not  all,  the  .somatic-cells  which 
arc  brought  in'.o  apposition  by  the  i^rat't  must  be 
supposed  thus  to  mi.\  thtir  nuclear  contents  at  the 
plane  of  the  i^raft ;  for  otherwise  the  hybi'id  would  not 
afterwards  present  equally  the  characters  of  stock  and 
scion.  Now,  there  may  be  hundreds  of  thousands  of 
such  cells,  and  therefore  it  seems  impossible  that  the 
facts  of  t^raft-hybridization  can  be  reconciled  with  the 
theory  of  L;erm-plasms  '. 

The  third  line  of  evidence  ac^ainst  this  theory — 
i.e.,  the  evidence  in  favour  of  the  transmission  of 
acquired  characters — is  to  constitute  the  subject- 
matter  of  future  chapters.  Therefore  it  will  here  be 
sufficient  tt)  adduce  only  one  fact  t)f  this  kind.  And 
I  select  it  because  it  is  one  that  has  b<,'en  dealt  with  by 
VVeismann  himself.  In  one  of  his  more  recent  state- 
ments he  sa)s  : — 

The  distinguished  botanist  De  Vrics  has  proved  that  certain 
constituents  of  the  cell  body  e.;,;.,  llie  chroniatuphores  ot 
.•\l;-jac  pass  directly  from  the  maternal  ovum  to  the  dauj^hter 
organism,  while  the  male  ^erm-cells  {generally  lontain  no 
chromatophores.  Here  it  appears  possible  tlial  a  transmission 
of  somatu'jenelic  variation  has  occurred  '". 


Now  althouLjh.  as  W'cismanii  i^ncs  on   to  observe, 

'  Possibly  the  sclujol  of  Wcisiiiaiiii  may  siiii|il\'  r(  fuse  to  accept  tlie 
f.icts,  which  arc  conrL'ssi<l]y  raic.  aiul,  iii  many  ot  llic  cases  allci^eii, 
(iul)ious.  In  ullier  easts,  however,  tlie  e\i(le!ice  is  sufficient  to  have 
salislied  tlie  caiilious  jiulj;cmeiit  of  |)ar\\in,  who  ha-.  <iiscus.-<e(i  it  in 
detail.  Tlierefore,  even  if  the  Meo-Darwiniaiis  reimdiue  llii>  evidence, 
ac  least  they  iiiii;lit  to  state  lli.it  sucli  is  liie  \  ositioa  wlaoh  ihey 
adojil. 

^  Aatwc,  Feb.  Otii,  iSyo. 

G  % 


m 


■M 


.  \. 


11  i 


I 


i 


84      An  Hxaniinatioii  of  Wcismaiuiism. 

'*  in  tlicsc  lower  plants,  the  scj)arati()n  between  somatic 
and  reproductive  cells  is  sli^dit,"'  in  the  facts  to  which 
he  alludes  we  appear  to  have  ^ood  evidence  of  an 
influence  excrcisetl  by  somatic  cells  upon  the  germinal 
contents  of  reproductive  cells.  And  if  such  an  influence 
is  capable  of  bcin;^  exercised  in  the  case  of  "  these 
lower  plants,"  it  follows  that  there  is  no  such  absolute 
separation  between  somatic  tissues  and  ^erm-plasm  as 
VVeismann's  theory  recpiires.  Moreover  it  follows 
that,  if  the  essential  distinction  between  ^erm-plasm 
and  somato-plasm  (or  "  somatic  idioplasm  ")  is  thus 
violated  at  the  very  foundation  of  the  multicellular 
orr][anisms.  there  ceases  to  be  any  a  priori  reason  for 
drawing  arbitrary  limits,  cither  as  to  the  level  of  organ- 
ization at  which  such  "  transmi.ssion  of  somatogenetic 
variation  has  occurred."  or  as  to  the  degree  of  detail 
into  which  it  may  extend.  ]?oth  these  matters  then 
.stand  to  be  tested  by  observation  ;  and  the  burden  of 
proof  lies  with  the  school  of  Weismann  to  show  at 
what  level  of  organization,  and  at  what  degree  of 
representation,  somatogenctic  changes  cease  to  repro- 
duce themselves   by  heredity. 

Passing  on,  then,  to  higher  levels  of  organization, 
and  therefore  to  higher  degrees  of  representation, 
I  shall  endeavour  to  show  that  this  burden  of  proof 
cannot  be  discharged.  For  I  shall  endeavour  to 
show,  not  merely,  as  just  shown,  that  there  ceases 
to  be  any  a  priori  reason  for  drawing  arbitrary 
limits  with  respect  either  to  levels  of  organization 
or  to  tlegrces  of  representation,  but  that,  as  a  matter 
of  fact,  there  are  no  such  limits  as  the  passage  above 
quoted  assigns.  On  the  contrar\'.  I  believe  there 
is  as   good   evidence  to    prove    the   not   unfrequent 


Wcismanns  theory  of  Heredity  (1891).    85 


transmission  of  acquired  ("  somatofrcnctic  ")  characters 
amonjT  the  higher  plants -and  even  among  the  higher 
animals — as  there  is  of  the  occurrence  of  this  phe- 
nomenon in  the  case  of  the  Alga  just  mentioned.  But 
in  order  to  do  this  evidence  justice,  I  shall  have  to 
take  a  new  point  of  de[)arture  and  consider  as  a 
separate  question  the  transmissibility  of  accjuired  char- 
acters. Meanwhile,  and  as  far  as  W^eismann's  theory 
of  heredity  is  concerned,  it  is  jnough  to  have  shown, — 
if  I  have  been  successful  in  doing  so, — that  not  only 
is  there  no  evidence  to  sustain  his  fundamental  postu- 
late touching  the  material  of  heredity  having  always 
occupied  a  separate  "sphere"  of  its  own  "since  the 
first  origin  of  life";  but  that  there  is  good  evidence 
to  prove  the  contrary.  For  whether  or  not  the  re- 
ciprocal action  of  "somato-i)lasm  "  and  "germ-plasm" 
can  ever  proceed  to  the  extent  of  causing  acquired 
characters  to  be  inherited  (so  as  to  produce  ''  repre- 
sentative congenital  changes  "),  all  that  is  distinctive 
in  this  theory  must  be  regarded  as  barren  speculation, 
unless  it  can  be  shown  that  the  foregoing  facts  have 
failed  to  prove  such  a  reciprocal  action  as  ever 
occurring  in  any  lower  degree  (so  as  to  produce 
"specialized  congenital  changes  "). 


':! 


I    I 


CHAITICR    IV. 

KXAMINATIOX    OV   Wf.ISMANN's   TiIKORY 
OK    lOVOLKTION   (  I -Si;  I  ). 

IIavixc.  now  considered  cfcrm-plasm  as  perpetually 
continuous.  \vc  have  next  to  regard  it  as  unalter- 
abl\'  stable. 

First,  let  it  be  noted  that  these  two  fundamental 
and  distinctive  postulates  of  the  whole  Weismannian 
system  are  so  intimate!}'  connected  as  to  be  in  lari^^e 
measure  mutually  dependent.  I"\-)r.  on  the  one 
hand,  if  u^erm-plasm  has  not  been  pcri)etually  con- 
tinuous since  the  Hrst  ori^rin  of  life,  it  cannot  have 
been  absolutely  stable  "since  the  Hrst  orit:jin  of  sexual 
propat^ation  " :  every  time  that  its  hereditary  characters 
are  mollified  by  its  containincj  soma  (whether  or 
not  represeniatively  so),  its  stability  has  been  so 
tar  upset.  On  the  other  hand,  if  L^erm-plasm  has 
not  been  ab.solntcly  stable,  it  cannot  have  been  per- 
petually continuous  ''since  the  first  origin  of  life." 
As  oftjen  as  its  stability  has  been  upset,  it.s  "  mo- 
lecular structure''  has  been  modified  by  gauscS-_<T^^ 
extra,  as  distinc^uished  from  mixtures  of  f^ermjj^)l;L?ms 
in  sexual  unions.  Therefore,  it  can  no  longer  have 
been  continuous  in  the  sense  of  having  borne  an 
ineffaceable  record  of  all  congenital  variations,  due  to 
sexual  unions^  throughout  the   entire   phylogeny    of 


IVcistnanns  theory  of  livolution  (1S91).    87 

the  Mctaphyt.i  and  Mcta/oa.  At  most  it  can  have 
been  continuous  only  in  the  attenuated  sense,  that 
however  much  and  however  often  its  herechtary 
characters  may  have  been  modified  by  somatic 
changes  on  the  one  hand  or  by  changes  in  tiie 
external  conditions  of  hfe  on  tlie  other,  they  can 
never  have  been  thus  modit'ied  rc[^rcscntatively,  as 
supposed  by  tiie  thet)ry  of  paiiLjenesis. 

l"*rom  which  it  follows  that,  while  examininij  in 
our  last  chapter  Wei.smann's  doctrine  ol  the  i)er- 
pctual  continuity  of  i^erm-plasm,  we  have  been 
ii.tlirectly  examinini,'  also  his  companion  doctrine  of 
the  unalterable  stability  of  germ-plasm.  Neverthe- 
less, for  the  sake  of  doing  justice  to  both  these 
doctrines.  I  have  thought  it  desirable  to  examine 
each  on  lis  own  merits,  without  prejudice  arising 
from  our  criticism  of  the  other.  To  such  a  .separate 
and  independent  examination  of  the  doctrine  of 
unalterable  stability  wc  will,  therefore,  now  proceed. 

As  we  have  already  and  repeatedly  seen,  this 
doctrine  of  the  unalterable  or  absolute  stability  of 
germ-plasm  "since  the  first  origin  of  sexual  propaga- 
tion" is  a  logically  es.sential  part  of  VVeismann's 
theory  of  evolution,  or  of  his  system  of  hypotheses 
consideretl  as  a  whole.  It  is  so  because  upon  this 
doctrine  de[)cnds  his  reference  of  individual  variations 
in  the  Meta/.oa  to  an  ultimate  origin  in  the  Protozoa, 
the  significance  of  sexual  reproduction  in  the  theory 
of  natural  selection.  &c.,  &c.  Therefore  this  doctrine 
of  the  absolute  stability  of  gcrm-[)lasm  is  enunciated 
by  Weismann,  not  merely  for  the  purpose  of  meeting 
any  one    class    of   facts,  such    as   tho.se  of   atavism 


I'' 


>' 
^ 


.t 


1 

Hi 

■A 

I 

J 

] 

i 

Ji 

pp 


'  i  I 


88      ylfi  Jixiwiiuation  of  U'eisfinviuism. 

pcrslstincc  of  rudinicntary  orfjans,  &c.  Tlie  doctrine 
is  enunciated  for  the  purpose  of  constituting  one  of 
the  foundation-stones  of  liis  ;^fcneral  tlieory  of  evolu- 
tion. We  have  now  to  consider  how  far  the  (juality 
of  this  stone  renders  it  trustworthy  as  a  basis  to  build 
upon. 

In  the  first  place,  wc  can  .scarcely  fail  to  perceive 
that  this  doctrine  of  the  absolute  stability  of  ^^erni- 
|)lasm  is  not  only  gratuitous,  but  intrinsically  imi)ro- 
bable.  That  the  most  complex  material  in  nature 
.should  likewi.se  be  the  most  .stable  is  oppo.sed 
to  all  the  ana!(^^ies  of  nature,  and  theref(jrc  to 
all  the   probabilities  of  the  case. 

Again,  the  ^a-rm-plasm,  as  it  oriujinaliy  occurred 
(and  .still  exists)  in  unicellular  or^janisms.  is  sujjposed 
to  be  exactly  the  same  kind  of  material  as  now 
occurs  in  the  ^crm-cells  of  multicellular  (.rjjanism.s. 
Yet  the  ver>'  same  theory  wiiich  suppo.ses  so 
absolute  a  stability  on  the  [)art  of  gerni-plasm 
when  located  in  y;erm-cells  (or  diffused  throu<^h 
somatic-cells),  likeui.se  supposes  so  hi<;h  a  de^jree  of 
variability  on  the  part  of  ^^erm-plasm  when  not  thus 
located,  as  to  represent  that  all  individual  variations 
which  have  ever  taken  place  in  the  unicellular 
ort,Mnisms — and  all  the  innumerable  species  of  such 
orL^anisms  which  have  arisen  therefrom — have  been 
due  to  the  direct  action  of  external  cond ijt ion sof_ life  ; 
or.  in  other  words,  to  the  instability  of  germ-plasin. 
The  very  same  substance  which  at  one  time  and  in  one 
place  is  supposed  to  be  .st)  absolutely  unchaufj^eable, 
at  another  time  and  in  another  place  is  supposed  to 
be  hiL^hly  susceptible  of  chan^jc. 

Lastly — and  this  is.  perhaps,  the  most  curious  part 


ll'cismanns  theory  of  Evolution  (1891).    S9 

of  the  whole  matter — the  place  where  ^erm-plasm  is 
supposed  to  be  unchangeable  is  not  the  place  where 
it  is  most  likely  to  be  so,  but  the  place  where  it  is 
least  likely.  For  ^'crin-plasm  as  it  occurs  in  the  ^crm- 
cells  of  multicellular  orijanisnis  must  have  a  constitu- 
tion greatly  more  complex  even  than  that  which  it  has 
in  unicellular  ori^anisms— seeing  that  in  the  former 
case,  and  by  hypothesis,  it  bears  a  living;  record  of  the 
whole  phylo{^'eny  of  the  Melaphyl.i  and  Meta/oa  in 
all  their  innumerable  branchin^rs.  And  not  only  so, 
but  when  germ-plasm  occurs  in  germ-cells  it  becomes 
exposed  to  much  greater  vicissitudes  :  its  environment 
has  become  vastly  more  complex,  aj>j\vell  as  greatb 
rnore  liable  to  change  with  the  changing  conditions  of 
life  of  the  many^  m..Lii!jle  species  in  which  it  resides, 
and  on  the  ir  ''vidual  somas  of  which  it  now  depends 
for  its  nourishment.  So  that,  altogether,  we  have  here 
on  merely  a  priori  grounds  about  as  strong  a  case 
against  this  doctrine  of  absolute  stability  as  it  is  well 
conceivable  that  on  merely  a  priori  grounds  a  case 
can  be. 

Turning  next  to  arguments  a  posteriori,  let  us  begin 
by  considering  those  which  \\  eismann  has  adduced  in 
support  of  the  doctrine. 

First,  he  alleges  that  there  is  a  total  absence  of 
variability  on  the  part  of  all  organisms  which  have 
been  produced  parthcnogcnctically.  t)r  from  unfer- 
tilized ova.  We  may  look  in  vain,  he  says,  for  any 
individual  differences  on  the  part  of  any  multi- 
cellular organisms,  which  have  been  brought  into  ex- 
istence independently  of  the  blending  of  germ-plasms 
in  a  previous  act  of  sexual  union.  Now,  u.ique.s- 
tionably,  if  this  statement  could  be  corroborated  by 


ilj 


■i,i± 


n 


J 

1.1) 


90      yin  Exavii nation  of  Weisinannis7n. 

sufficiently  extensive  observation,  the  fact  would 
become  one  of  immense  si[^nificancc  — so  much  so, 
indeed,  that  of  itself  it  would  ^o  far  to  neutralize  all 
antecedent  objections,  and  to  verify  his  theory  as  to 
sexual  propaL;jation  being  the  sole  cause  of  coni^enital 
variation.  Ikit  seeing  that  the  alleged  fact  stands  so 
entirely  out  of  analogy  with  the  phenomena  of  bud- 
variation  (which  will  be  alluded  to  later  on),  it  is 
highly  improbable,  even  on  antecedent  grounds;  while 
Professor  Vines  has  refuted  the  statement  on  grounds 
of  actual  fact.  Thus,  speaking  of  the  Basidiomycetes^ 
he  says — 

These  Fiinj;i  are  not  .)nly  entirely  a-scxual,  but  it  would  appear 
that  they  have  been  evolved  in  a  purely  a-scxual  manner  from 
a-sexual  ascomycetous  or  ;ucidiomycetous  ancestors.  The 
Uasidiomycetcs,  in  fact,  affonl  an  example  of  a  vast  family  of 
plants,  of  the  most  varied  form  and  habit,  including  hundreds 
of  genera  and  species,  in  which,  so  far  as  minute  and  long- 
continued  investigation  has  shown,  there  is  not,  and  probably 
never  has  been,  any  trace  of  a  sexual  process  '. 

Here,  then,  we  have  actual  proof  of  "hereditary 
individual  variations"  among  a-sexually  propagating 
organisms,  sufficient  in  amount  to  have  given  origin, 
not  merely  to  ''individual  differences."  but  to  in- 
numerable speci3s,  and  even  genera.  Consequently 
Weismann  allows  that  the  criticism  abolishes  this  line 
of  evidence  in  favour  of  the  absolute  stability  of  germ- 
plasm  '-.  Consquently.  also,  wc  must  now  add,  in 
whatever  measure  the  alleged  fact  would  have  corro- 
borated  the  theory  had  it  been  proved  to  be  a  fact, 
in  that  measure  is  the  theory  discredited  by  proof  that 

*  Nature,  vol,  xl.  p.  626. 
'  Ibiii.,  vol.  xH.  p.  33a. 


IVeisfuann's  theory  of  Evolution  (1891).    91 

it  is  not  a  fact.  For,  if  tlie  theory  were  sound,  this 
particular  fact  would  certainly  have  admitted  of  de- 
monstration :  therefore  the  proof  that  it  is  not  a  fact 
— but  the  reverse  of  a  fact — amounts  at  the  same  time 
to  a  disproof  of  the  theory  ^. 

The  only  other  line  of  evidence  to  be  adduced  in 
favour  of  the  absolute  stability  of  <:(crm-plasni  is  that 
which  is  furnished  by  the  hiL;"h  antitjuity  of  some  specific 
ty[)es,  by  the  facts  of  atavism,  and  by  the  persistency 
of  vcstit;ial  orij^ans.  But  this  line  of  evidence  is  as 
futile  as  the  other.  Nobody  has  ever  questioned 
that  hereditary  characters  are  persistently  stable  as 
lontf  as  they  arc  persistently  maintained  by  natural 
selection  ;  and  this.  accordiuLj  to  Weismann  himself, 
must  have  been  th"  case  with  all  lon<^-endurini^ 
species :  these,  therefore,  fail  to  furnish  any  evidence 
of  the  inJicrcni  stability  of  germ-[)lasm,  which  is  the 
only  point  in  question. 

Ai^ain,  as  ret^ards  the  facts  of  atavism,  nobody  is 
disputing  these  facts.  What  we  are  disputing  is 
whether  the  degree  of  inherent  stability  which  they 
uncjuestionably  prove  can  be  rationally  regarded  as 

'  In  his  Essays  (vol.  i.  p.  2^2^  Wiismann  snys: — "  If  it  could  he  shown 
that  a  purely  imrtheiiogenctic  si)cci(.s  hnd  hccome  transformed  into  a 
new  one,  such  an  observation  would  i^rove  the  existence  «)f  some  m  w 
force  of  transformation  otlier  than  seleetivc  processes,  for  the  new  species 
could  not  have  been  produced  by  these  latter."  lUit  now  it  has  been 
shown  that  a  ]nnely  ]iartlKiiot;enetic  specii  s  can  bi'  transformed  into 
a  new  one,  and  tiierefore  it  seems  desiralilc  to  note  tliat  the  observation 
does  not  so  much  as  tend  to  prove  the  existence  of  some  iicw  force 
of  transformation  other  than  selective  prc::esscs.  Fortius  most  singular 
statement  can  only  stand  on  a  prior  aci:eptance  of  \\  eismaim's  f)wn 
assum|)tion,  as  to  ajiij^hij^ony  lieini^  the  only  possible  cause  of  indivi(hial 
hereditary  variation.  Only  if  we  have  already,  and  wilii  aljsolute 
certainty,  embraced  the  whole  Weismamii;\n  creed,  could  we  consent  to 
aftirm  that  "  natural  selection  is  an  impossiLiility  in  a  species  propagated 
by  a-sexual  repioiluclion." 


H^X 


92      An  Examination  of  Weismamiism. 

such  that  it  may  endure,  not  merely  for  such  a  com- 
paratively small  number  of  generations  as  these  facts 
imply,  but  actually  for  any  number  of  generations, 
or  through  the  practically  infinite  series  of  generations 
that  now  intervene  between  the  higher  metazoa  and 
their  primeval  parentage  in  the  protozoa.  Clearly, 
the  ratio  between  these  two  things  is  such  that  no 
argument  derived  from  the  facts  of  at  ivism  can  be 
of  any  avail  Tfor  the  purposes  of  this  VVeismannian 
doctrine. 

Lastly,  as  regards  vestigial  organs,  the  consideration 
that,  surprisingly  persistent  as  they  unquestionably  are, 
nevertheless  they  do  eventually  disappear,  seems  to 
prove  that  the  power  of  heredity  does  in  time  become 
exhausted,  even  in  cases  most  favourable  to  its  con- 
tinuance. That  it  should  thus  become  finally  ex- 
hausted is  no  more  than  Darwin's  theory  of  perishable 
gemmules,  or  Galton's  theory  of  a  not  absolutely 
stable  stirp,  would  expect.  But  the  fact  is  irre- 
concilable with  Wcismann's  theory  of  an  absolutely 
stable  germ-plasm. 

Hence,  we  can  only  conclude  that  there  is  no 
evidence  in  favour  of  the  hypothesis  that  germ-plasm 
has  been  unalterably  stable  "since  the  first  origin 
of  sexual  propagation";  while  the  suggestion  that 
it  may  have  been  so  is  on  antecedent  grounds  im- 
probable, and  on  inductive  grounds  untenable.  It 
only  remains  to  add  that  the  dc^'ee  of  stability 
has  been  proved  in  not  a  few  cases  to  be  less  than 
even  the  theory  of  gemmules  might  anticipate.  Many 
facts  in  proof  of  this  statement  might  be  given,  but  it 
will  here  suffice  to  quote  one,  which  I  select  because 
it  has  been  dealt  with  by  Professor  Weismann  himself. 


lelf. 


Weismanns  theory  of  Evolution  (1891).   93 

Professor  Hoffmann  has  published  an  abstract  of 
a  research,  which  consisted  in  subjecting;  plants  with 
normal  flowers  to  changed  conditions  of  life  through 
a  series  of  generations.  In  course  of  time,  certain  well- 
marked  variations  appeared.  Now,  in  some  cases  such 
directly-produced  variations  were  transmitted  by  seed 
from  the  affected  plants  ;  and  therefore  Weismann 
acknowledges,—"  I  have  no  doubt  that  the  results  are, 
at  any  rate  in  part,  due  to  the  operation  of  heredity." 
Hence,  whether  these  results  be  due  to  the  trans- 
mission of  somatogenetic  characters  ("  representative 
changes"),  or  to  the  direct  action  of  changed  conditions 
of  life  on  the  germ-plasm  itself  ("  specialized  changes"), 
it  is  equally  certain  that  the  hereditary  characters 
of  the  plants  were  congenitally  modified  to  a  large 
extent,  within  (at  most)  a  few  generations.  In  other 
words,  it  is  certain  that,  if  there  be  such  a  material  as 
germ-plasm,  it  has  been  proved  in  this  case  to  have 
been  highly  unstable.  Therefore,  in  dealing  with 
these  and  other  similar  facts,  Weismann  himself  can 
only  save  his  postulate  of  continuity  by  surrendering 
for  the  time  being  his  postulate  of  stability  ^. 

If  to  this  it  be  replied  that  Hoffmann's  facts  are 
exceptional— that  Gartner,  Niigeli,  De  Candolle,  Peter, 

'  What  he  says  is : — "  It  was  only  after  a  preritcr  or  less  number 
of  {jenerations  ha<l  elajiscd  ihat  a  vaiinhle  ]  rojiortion  of  douljle  flowers 
appeared,  sometimes  accompanied  liy  ciianL,'es  in  ifie  leaves  and  in  the 
colours  of  the  flowers.  'I'liis  fact  adniils  of  oily  one  ititcypyctation  : — 
the  changed  conditicms  at  first  produceii  slii^lit  and  in(.tTeciual  changes 
in  the  idio-plasm  of  the  individual,  which  was  transmitted  to  the  following 

generation Now,  the  idio-plasm  of  the   fust   iintugtnclic  giaoe 

(VIZ.,  germ-plasm  alone  passes  from  one  generation  to  another,  and 
hence  it  is  clear  that  the  germ-plasm  itself  must  have  been  gradually 
changed  by  the  conditions  of  life,  until  the  alteration  became  sufficient  to 
produce  changes  in  the  soma,  whicli  appeared  as  visible  characters  in 
either floiver  or  leafy — l\ssays,  pp.  42O-7  j  italics  nuue. 


I 


»■ 


M 


\i 


i 


1 


!i 


94      An  Examination  of  Weismannism. 

Jordan,  and  others,  did  not  find  individual  variations 
produced  in  plants  by  chan<;cd  conditions  of  life  to 
be  inherited, — the  reply  would  be  irrelevant.  It  does 
not  require  to  be  proved  that  all  variations  produced 
by  chanijed  conditions  of  life  are  inherited.  If  only 
some — even  thou^^h  it  be  but  an  extremely  small 
pcrcentac,^e — of  such  variations  are  proved  to  be 
inherited,  the  many  millions  of  years  that  separate 
the  i^erm-plasm  of  to-day  from  its  supposed  origin 
in  the  protozoa,  must  have  furnished  opportunities 
enoucfh  for  the  occurrence  of  such  variations  to  have 
obliterated,  and  re-obliterated  numberless  times,  any 
aborii^inal  differences  in  the  j^crm-plasms  of  in- 
cipiently  sexual  organisms.  Moreover,  it  is  probable 
that  when  further  experiments  shall  have  been  made 
in  this  direction,  Hoffmann's  results  will  be  found 
not  so  exceptional  as  they  at  present  appear. 
Mr.  Mivart,  for  example,  has  mentioned  several 
instances '  ;  while  there  are  not  a  few  facts  of 
gener^v'  knowledge — such  as  the  modifications  under- 
gone by  certain  Crustacea  as  a  direct  result  of 
increased  salinity  of  the  water  in  which  they  live — 
that  will  probably  soon  be  proved  to  be  facts  of  the 
same  order.  lUit  here  attention  must  be  directed 
to  another  large  body  of  facts,  which  are  of  high 
importance  in  the  present  connexion. 

The  phenomena  of  what  is  called  bud-variation  in 
plants  are  phenomena  of  not  infrequent  occurrence, 
and  they  consist  in  the  sudden  ap[)earance  of  a 
peculiarity  on  the  part  of  a  shoot  which  develops 
from  a  single  bud.  When  such  a  peculiarity  arises, 
it  admits  of  being  propagated,  not  only  by  cuttings 
'  Nature,  Nov.  14,  i88y,  p.  41. 


Wei s maun  s  theory  of  Evolution  (1891).    95 


a 


and  by  other  buds  from  that  shoot,  but  sometimes 
also  by  seeds  which  the  flowers  of  the  shoot  sub- 
sequently   produce  —  in    wliich    case    all     the    laws 


)f  inhei 


thj 


ritance  tnat  apply  to  conLjenitai  vanatums 
are  found  to  apply  also  to  bud-variation.  Or,  as 
Darwin  puts  it,  ''  there  is  not  any  particular  in  which 
new  characters  arising  by  bud-variati(jn  can  be  dis- 
tinguished from  those  due  to  seminal  variation " ; 
and,  therefore,  any  theory  which  deals  with  the  latter 
is  bound  also  to  take  cognizance  of  the  former.  Now, 
as  far  as  I  can  fuid,  there  is  only  one  paragrai)h  in 
which  Weismann  alludes  to  bud-variation,  and  what 
he  there  says  I  do  nut  find  very  easy  to  understand. 
Therefore  I  will  quote  the  whole  paragraph  verbatim. 

I  have  not  hitherto  consiilcred  budding  in  relation  to  my 
theories,  but  it  is  obvious  tliat  it  is  to  l)e  explained,  from  my 
point  of  view,  by  sujjposinj,'  tliat  the  t;enn-pkisin  which  passes 
on  into  a  butldini;  indiviilual  consists  not  only  of  tiie  un- 
changed germ-pl.ism  of  the  first  ontogenetic  stage,  but  of  this 
substance  altered,  so  far  as  tt)  correspond  with  the  altered 
structure  of  the  indivitlual  which  arises  from  it -viz.,  the  root- 
less shoot  which  sjjrings  from  the  stem  or  branches.  Th:; 
alteration  must  be  very  slight,  and  perhaps  c|uite  insignificant, 
for  it  is  possii)le  that  the  differences  between  die  secondary 
shoots  and  the  primary  plant  may  cepend  chiefly  o.  the  changed 
conditions  of  development,  which  takes  place  lieneath  the 
earth  in  the  latter  case,  and  in  the  tissues  of  the  plant  in  the 
former.  Thus  we  may  ''^lagine  that  the  idio-plasm  |.'  of  that 
particular  budj,  when  itdc.elops  into  a  (lowering  shoot,  produces 
at  the  same  time  the  germ-celis  which  are  found  in  the  latter. 
We  thus  approach  an  understanding  of  Fritz  Miiller's  obser- 
vation ;  for  if  the  whole  shoot  which  produces  the  tlower  arises 
from  the  same  idio-plasm  which  also  forms  its  germ-cell^,  we  can 
readily  understand  why  the  latter  should  cont.iin  the  same 
hereditary  tendencies  which  were  previously  expressed  in  the 
tiower   which   produced  them.     The   fact  that   variations  may 


'    M 


;ii 


i  If 


it' 


■i! 


\i  'i  \ 


iii  ■ 


96      An  lixainination  of  Weismannism. 

occur  in  ;i  single  shoot  depends  on  the  changes  explained  above, 
which  occur  in  the  idio-plasni  durin},'  the  course  of  its  growth, 
as  a  result  of  the  varying  proportions  ir  (which  the  ancestral 
idio-plasms  may  be  contained  in  it '. 

The  meaniiiL^  here  appc;ir.s  to  be  twofold.  For 
there  are  only  two  ways  of  explaining  the  phenomena 
of  biid-vaiiation.  Either  they  are  due  to  the  influ- 
ence of  external  conditions  actini^  on  the  particukir 
bud  in  question,  or  else  they  are  due  to  so-called 
"spontaneous"  chan<jes  taking  place  within  the  bud 
itself.  Possibly  it  may  be  both,  but  at  least  it  must 
be  either.  Well,  in  the  above  passage,  Weismann 
appears  to  assume  that  it  is  both.  For  at  the  begin- 
ning of  the  passage  he  speaks  of  the  "  germ- plasm  of 
the  first  ontogenetic  stage "  becoming  "  altered  so 
far  as  to  correspond  with  the  altered  structure  of  the 
individual  which  arises  therefrom,"  and  he  goes  on 
to  say  that  the  alteration  "  may  depend  chiefly  on 
the  changed  conditions  of  development " — that  is,  as 
I  understand,  the  influence  of  external  conditions. 
But  at  the  end  of  the  paragraph  he  says  that  "  the 
changes  which  occur  in  the  idio-plasm  during  the 
course  of  its  growth  "  in  the  sporting  bud,  are  due  to 
"  the  varying  proportions  in  which  the  ancestral  idio- 
plasms  may  be  contained  in  it."  Thus,  I  take  it, 
Weismann  here  entertains  both  explanations  of  the 
phenomena  in  question  :  he  appears  to  regard  these 
phenomema  as  partly  due  to  peculiar  adm'xtures  of 
ancestral  idio-plasms  in  the  bud  itself  (or  ''spon- 
taneous "  variation),  but  partly  also  to  an  alteration 
of  the  germ-plasm  by  its  changed  condition  of  develop- 
ment (or  variation  caused  by  external  conditions;), 

*  Essays,  ind  Ed.,  pp.  331-3. 


above, 
rowth, 
ccslral 

For 

)mcna 
influ- 
ticukir 
-called 
\e  bud 
t  must 
ismann 
bcgin- 
iasm  of 
red    HO 
2  of  the 
roes  on 
cfly  on 
is,  as 
itions. 
;  '-the 
the 
due  to 
al  idio- 
take  it, 
of  the 
d  these 
:ures  of 
"  spon- 
:eration 
levelop- 


ng 


Weismaiius  theory  of  Evolution  (1891).    97 

However,  it  is  but  of  little  consequence  whether  or 
not  this  is  the  meaning  which  Weismann  intends  to 
convey.  For  the  point  we  are  coming  to  is,  that, 
whatever  he  intends  to  convey,  **  from  the  point  of 
view  "  of  the  theory  of  germ-plasm,  there  is  only  otic 
interpretation  possible.  It  is  not  open  to  Weismann 
(as  it  was  to  Darwin,  or  even  to  Galton,)  to  entertain 
both  the  explanations,  whether  separately  or  in  con- 
junction. For  germ-plasm  (unlike  gemmules,  or  even 
stirp)  must  be  held  always  and  everywhere  unalterably 
stable :  else  the  whole  superstructure  of  Weismann's 
theory  of  evolution  falls  to  the  ground.  We  cannot 
consent  to  his  retaining  this  theory  on  the  one  hand, 
and,  on  the  other,  explaining  bud-variation  by  "germ- 
plasm  of  the  first  ontogenetic  stage "  becoming 
altered  "chiefly  by  changed  conditions  of  develop- 
ment." Even  if  it  were  true  that  "  the  alteration 
must  be  very  slight,  if  not  quite  insignificant,"  there 
would  here  be  a  rift  in  the  lute,  which  must  finally 
stop  any  further  harping  on  the  subject  of  Evolution. 

From  the  point  of  view  of  this  theory,  then,  there 
is  only  one  interpretation  open, — viz.,  that  a  bud- 
variation  is  ultimately  due  to  a  peculiar  admixture 
of  germ-plasms  in  the  seed  from  which  the  bud  was 
ultimately  derived.  But  the  objections  to  entertaining 
this  as  even  a  logically  possible  explanation  of  the 
phenomena  in  all  cases,  is  insuperable. 

In  the  first  place,  such  a  variation,  when  it  does 
arise,  is  usually  a  variation  of  an  extremely  pronounced 
character ;  therefore  it  is  very  far  from  supporting 
Weismann's  view,  that  the  "  alteration  "  of  germ-plasm 
which  is  needed  to  produce  it  '*  must  be  very  slight, 
and  perhaps  quite  insignificant."     In  most  cases  where 

U 


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i1 


H, 


tt. 


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i 


Hi. 


98     An  Bxamina/jon  of  Wetsmannisnt. 

it  occurs  bud- variation  presents  so  extreme  a  departure 
from  the  normal  type,  that  no  other  kind  of  variation 
can  be  fitly  compared  with  it  in  this  respect.  In 
particular,  the  degree  of  variation  is  usually  very 
much  greater  than  that  which  customarily  obtains  in 
congenital  vai  iations  of  the  ordinary  kind  ;  and.  there- 
fore, if  there  be  supposed  due  to  particular  admixtures 
of  germ-plasm  in  sexual  propagation,  much  more 
must  those  admixtures  which  give  rise  to  sporting 
buds  be  characterized  by  peculiarities  of  no  "insigni- 
ficant "  order.  And  much  more,  therefore,  ought 
they  to  assert  themselves  in  sister-buds  developed 
from  the  same  individual  seed  (ovule),  than  we  find 
to  be  the  case  with  any  sister-organisms  which  are 
developed  from  different  individual  seeds.  Yet,  in  the 
second  place,  so  far  is  this  from  being  the  case,  that 
the  most  remarkahie  feature  connected  with  bud- 
variation — next  to  the  suddenness  and  extreme  amount 
of  the  variation  itself — is  the  usually  isolated  nature 
of  its  occurrence.  There  mav  be  thousands  of  other 
buds  on  the  same  plant,  and  yet  it  is  one  bud  alone 
that  deviates  so  suddenly  and  so  widely  from  its 
ancestral  characters.  Nay,  more,  a  single  bud-varia- 
tion may — and  usually  does — occur  in  plants  which 
are  habitually  propagated  by  cuttings  and  graftings  ; 
so  that  there  may  not  only  be  thousands,  but  millions 
of  buds  all  derived  from  one  original  seed,  and  all  for 
many  years  remaining  perfectly  true  to  their  parent 
type,  with  the  single  exception  of  the  sporting  bud, 
which,  while  it  departs  so  widely  from  that  t}'pe,  is 
usually  capable  of  transmitting  its  extraordinary  char- 
acters indefinitely  by  a-sexual,  and  not  infrequently 
also  by  sexual,  methods.     So  that,  altogether,  it  seems 


«  r  »  •  ' 


•ture 

ition 
In 

very 

ins  in 

;here- 

ctures 

more 

orting 

isigni- 

ought 

eloped 

/c  find 

ich  are 

,  in  the 

se,  that 

h   bud- 
mount 
nature 
f  other 
d  alone 

[rom  its 
varia-  . 
which 
laftings ; 
millions 
all  for 
parent 
ing  bud, 
I  type,  is 
[ry  char- 
jqucntly 
lit  seems 


Weisnmuns  theory  of  Evolution  {1891).    99 

impossible  to  suppose  that  in  millions  and  millions  of 
sister-buds,  which  through  years  and  years  exhibit  no 
variation,  a  highly  peculiar  admixture  of  germ-plasm 
(which  was  originally  present  in  the  parent-seed) 
should  have  been  latent ;  that  it  should  then  suddenly 
become  so  patent  in  a  single  bud,  after  which  it  never 
occurs  in  any  other  bud,  save  in  the  progeny  of  the 
sporting  one. 

On  the  whole,  then,  while  it  thus  seems  impossible 
to  attribute  all  cases  of  bud-variation  to  mixtures  of 
germ-plasms  in  sexual  propagation,  the  theory  of 
germ-plasm  is  unable  to  entertain  any  other  explana- 
tion, on  pain  of  surrendering  its  postulate  touching 
the  unalterable  stability  of  germ-plasm,  on  which  the 
Wcismannian  theory  of  evolution  is  founded. 

So  much  for  Weismann's  evidence  touching  the 
extreme,  or  virtually  everlasting,  stability  of  germ- 
plasm.  We  have  seen  that  this  evidence  is  not  merely 
of  a  very  poor  character  per  st\  or  on  antecedent 
grounds ;  but  that  it  is  directly  negatived  as  evidence 
by  the  a-sexual  origin  of  species  in  the  plants  alluded 
to  by  Professor  Vines  ;  by  certain  facts  which  prove  so 
high  a  degree  of  instability  on  the  part  of  this  hypo- 
thetical substance,  that  in  some  cases  it  admits  of 
being  very  considerably  modified  in  the  course  of 
only  two  or  three  generations  by  exposure  to  changed 
conditions  of  life  ;  while  in  other  cases  it  may  "'  sport," 
so  as  to  produce  "  hereditary  individual  variations," 
which  are  much  more  pronounced  than  any  of  those 
that  ordinarily  result  from  a  blending  of  hereditary 
qualities  in  an  act  of  sexual  union. 

It   will  be  well   to  conclude  our    examination   of 

H  2 


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lOo      -<4«  Examination  of  Weisniannism. 

Wcismann's  system  by  statinj^  exactly  the  effect 
produced  on  his  theory  of  evolution  by  the  foregoing 
disproof  of  its  fundamental  postulate — the  absolute 
stability  of  germ-plasm. 

Clearly,  in  the  first  place,  if  germ-plasm  has  not 
been  absolutely  stable  "since  the  first  origin  of  sexual 
propagation,"  the  hereditary  characters  of  germ-plasm 
may  have  been  modified  any  number  of  times,  and 
in  always  accumulating  degrees.  It  matters  not 
whether  the  modifications  have  been  due  mainly  to 
external  or  to  internal  causes.  It  is  enough  to  have 
shown  that  modifications  occur.  For,  it  will  be  re- 
membered, the  doctrine  of  the  absolute  stability  of 
germ-plasm  is,  that  inasmuch  as  the  "molecular" 
structure  of  germ-plasm  cannot  be  affected  either 
from  without  or  from  within,  the  only  source  of 
"hereditary  individual  variations"  is  to  be  found  in 
admixtures  of  germ-plasms  taking  place  in  sexual 
fertilization.  Slight  "  molecular  "  differences  having 
been  originally  impressed  ui)on  different  masses  of 
germ-plasm  when  these  were  severally  derived  from 
their  unicellular  sources,  so  unalterable  has  been  the 
stability  of  germ-plasm  ever  since,  that  these  slight 
'•molecular"  differences  have  never  been  in  any 
degree  effaced  ;  and  although  in  sexual  unions  they 
have  for  untold  ages  been  obliged  to  mix  in  ever- 
varying  proportions,  they  still  continue — and  ever 
must  continue — to  assert  themselves  in  each  ontogeny. 
Therefore,  as  Weismann  himself  formulates  this 
astonishing  doctrine, — "  The  origin  of  hereditary  in- 
dividual variations  cannot  indeed  be  found  in  the 
higher  organisms,  the  Metazoa  and  Metaphyta  ;  but 
is  to   be   sought  for   in  the  lowest — the  unicellular 


WcisjJianns  theory  of  Evolution  (1891).    10 1 


orcranisms. 


»» 


Or  aj^ain, —  **  The  formation  of  new 
species,  which  amoni^  the  lower  Protozoa  could  be 
achieved  without  amphigony,  could  only  be  attained 
by  means  of  this  process  in  the  Metazoa  and  Mcta- 
phyta.  It  was  only  in  this  way  that  hereditary 
individual  differences  could  arise  and  persist  ^" 

Now  this  doctrine  is  the  most  distinctive,  as  it  is 
the  most  original  feature  in  Weismann's  system  of 
theories.  That  it  is  of  interest  as  an  example  of 
boldly  carrying  the  premises  of  a  theory  to  their 
logical  termination,  no  one  will  deny.  But  as  little 
can  it  be  denied  that  the  very  stringency  of  this  logical 
process  brings  the  theory  itself  into  collision  with  such 
facts  as  those  which  have  now  been  stated,  and  which, 
as  far  as  I  can  see,  are  destructive  of  the  theory — or. 
at  any  rate,  of  all  that  side  of  the  theory  which 
depends  on  the  doctrine  of  absolute  stability. 

Take,  for  instance,  the  sequent  doctrine  that  natural 
.selection  is  inoperative  among  the  unicellular  or- 
ganisms. Here,  indeed,  we  have  another  of  those 
doctrines  which  are  so  improbable  on  merely  ante- 
cedent grounds,  that  their  presence  might  well  be 
deemed  a  source  of  irremediable  weakness  to  the 
whole  theory  of  evolution  of  which  they  form  integral, 
or  logically  essential,  parts.  For  seeing  that  the 
rate  of  increase  in  most  of  the  unicellular  organisms 
is  quite  as  high  as — and  in  most  cases  very  much 
higher  than— the  rate  that  obtains  in  any  of 
the  multicellular,  it  becomes  on  merely  antecedent 
grounds  incredible  that  the  struggle  for  existence 
should  here  7iot  lead  to  any  survival  of  the  fittest. 
When,    for   instance,   we    learn    from    Maupas   that 

'  Essays,  p.  296. 


tl 


r^^ 


III  fi 
\\ 


!   'I 


'I 


it 


I 


I02      An  Exa)fn'ualion  of  IVcismannism. 

a  sincjlc  Stj'lonichia  is  potentially  cajvible  of  yield- 
ing a  billion  descendants  vvitliin  a  week,  we  should 
need  some  extraordinarily  good  evidence  to  make 
us  believe  that  as  regards  this  organism  natural 
selection  is  inoperative.  Hut  the  point  at  present  is 
that,  quite  apart  from  all  general  and  a  p-iori  con- 
siderations of  this  kind,  VVeismann's  doctrine  that 
unicellular  organisms  cannot  be  influenced  by  natural 
selection  must  be  abandoned.  I^'or  this  doctrine 
followed  deductivcl}'  from  the  premiss  that  in  the 
multicellular  organisms  congenital  variations  can  only 
be  due  to  admixtures  of  germ-plasms  in  acts  of 
sexual  fertilization  ;  so  that,  in  the  absence  of  such 
admixtures,  there  could  be  no  material  for  natural 
selection  to  work  upon.  But  now  we  have  found  that 
this  premiss  must  be  given  up  ;  and,  therefore,  the 
deduction  with  resi)ect  to  the  unicellular  organisms 
falls  to  the  ground.  Although  it  is  true  that  the 
unicellular  organisms  propagate  by  fission,  and 
although  we  grant,  for  the  sake  of  argument,  that 
they  never  propagate  by  way  of  sexual  unions — even 
so  this  can  no  longer  be  taken  to  argue  that  none  of 
their  innumerable  species  owe  their  origin  to  natural 
selection.  And,  although  it  is  probably  true  that  the 
sexual  methods  of  propagation  constitute  one  source 
of  hereditary  individual  variation  among  the  multi- 
cellular organisms,  there  is  no  vestige  of  any  indepen- 
dent reason  for  supposing  that  this  is  the  only  source 
of  such  variation ;  while  the  sundry  facts  which  have 
now  been  given  amount  to  nothing  short  of  a  demon- 
stration to  the  contrary  ^ 

'  In  this  connexion  it  oui.',hl  to  be  observed  that  Darwin  believed 
the  causes  of  variation  to  be  internal  as  well  as  external — or  arising 


Summary, 


103 


Lastly,  and  as  rejijards  the  multicellular  organisms, 
it  is  evident  that  VV'eismann  s  essay  On  the  Sii^iiijkatice 
of  Sexual  Reproduction  in  the  Theory  of  Natural 
Seleetion  must  be  cancelled.  For,  apart  from  the 
contradictory  manner  in  which  this  matter  has  been 
stated  (pp.  70,  93,  notes),  and  apart  also  from  the  con- 
sideration that  other  and  quite  as  probable  reasons 
have  been  suj^Ljcstcd  for  the  oriffin  of  sexual  repro- 
duction, there  is  the  fact  that  W'cismann's  theory  is 
no  longer  tenable  after  the  above  destruction  of  its 
logical  postulate  in  the  absolute  stability  of  germ- 
plasm.  For,  in  the  absence  (jf  this  postulate,  there  is 
no  basis  for  the  theory  that  admixtures  of  germ- 
plasms  in  sexual  reproduction  furnish  the  sole  means 
whereby  heritable  variations  can  be  supplied  for  the 
working  of  natural  selection. 

Summary. 

The  theory  of  ^erm-plasm  is  not  only  a  theory  of 
heredity  :  it  is  also,  and  more  distinctively,  a  theory 
of  evolution.  As  a  theory  of  heredity  it  is  grounded 
on  its  author's  fundamental  postulate  — the  continuity 
of  germ-plasm  ;  and,  further,  on  a  fact  well  recog- 
nized by  all  other  theories  of  heredity,  which  he 
expresses  by  the  term  stability  of  germ-plasm.  But 
as  a  theory  of  evolution  it  requires  two  additional 
postulates  for  its  support — viz.,  thai  germ-plasm  has 

from  "the  nature  of  the  organism"  no  less — or  cveti  more — than  from 
"changed  conditions  ot  lile."  But  altliuugh  he  appears  to  have  enter- 
tained the  a(hnixture  of  hereditary  endowments  in  sexual  unions  as  one 
of  the  causes  of  variation  belonging  to  the  former  category,  he  expressly 
says  that  he  did  not  ri-gardit  as  the  only,  or  even  the  main,  cause.  (Sec 
Variation,  &c.,  vol.  i,  pp.  197,  39S ;  vol.  ii,  pp.  337,  35a.) 


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104     An  Examination  of  Weismannism. 

been  perpetually  continuous  "  since  the  first  origin  of 
life,"  and  absolutely  stable  "  since  the  first  origin  of 
sexual  reproduction."  It  is  clear  that  these  two 
additional  postulates  are  not  needed  for  his  theory  of 
heredity,  but  only  for  his  additional  theory  of  evolu- 
tion. There  have  been  other  theories  of  heredity, 
prior  to  this  one,  which,  like  it,  have  been  founded  on 
the  postulate  of"  continuity  "  (in  Weismann's  sense)  of 
the  substance  of  heredity;  but  it  has  not  been  needful 
for  any  of  these  theories  to  postulate  further  that  this 
substance  has  been  alivays  thus  isolated,  or  even  that 
it  is  now  invariably  so.  For  even  though  the  isolation 
be  frequently  invaded  by  influences  of  body-changes 
on  the  congenital  characters  of  this  substance,  it  does 
not  follow  that  the  body-changes  must  be  transmitted 
to  offspring  exactly  as  they  occurred  in  parents.  They 
may  produce  in  offspring  what  we  have  agreed  to  call 
"  specialized  "  hereditary  changes,  even  if  they  never 
produce  ''representative"  hereditary  changes, — i.e., 
the  transmission  of  acquired  characters.  But  it  is 
essential  to  Weismann's  theory  of  evolniion  that  body- 
changes  should  not  exercise  a  modifying  influence 
ot  any  kind  on  the  ancestral  endowments  of  this 
substance ;  hence,  for  the  purposes  of  this  further 
theory  he  has  to  assume  that  germ-plasm  presents, 
not  only  eontinuity^  but  continuity  unbroken  since  the 
first  origin  of  life. 

Similarly  as  regards  his  postulate  of  the  stability  of 
germ-plasm  as  absolute.  It  is  enough  for  all  the 
requirements  of  his  theory  of  heredity,  that  the  sub- 
stance in  question  should  present  the  high  degree  of 
stability  which  the  facts  of  atavism,  persistence  of 
vestigial  organs,  &c.,  prove  it  to  possess.     But  for  his 


SMmmary, 


105 


further  theory  of  e^'olutnn  it  is  necessary  to  make 
this  further  postulate  of  the  stability  of  germ-plasm 
as  undisturbed  since  the  first  origin  of  sexual  propaga- 
tion :  otherwi.  there  would  be  no  logical  foundation 
for  any  of  the  distinctive  doctrines  which  go  to 
constitute  that  theory. 

Thus  much  understood,  we  proceeded  to  examine 
the  theory  of  germ-plasm  in  each  of  its  departments 
separately — i.e.,  first  as  a  theory  of  heredity,  and 
next  as  a  theory  of  evolution.  And  we  begun  by 
comparing  it  as  a  theory  of  heredity  with  the  prj- 
ceding  theories  of  Darwin  and  Galton.  In  the  result 
we  found  that  germ-plasm  resembles  gemniulcs  in  all 
the  following  respects.  It  is  particulate ;  constitutes  the 
material  basis  of  heredity;  is  mainly  lodged  in  highly 
specialized  cells ;  is  nevertheless  also  distributed 
throughout  the  general  cellular  tissues,  where  it  is 
concerned  in  all  processes  of  regeneration,  repair,  and 
a-sexual  reproduction ;  presents  an  enormously  com- 
plex structure,  in  that  every  constituent  part  of 
a  potentially  future  organism  is  represented  in  a  fer- 
tilized ovum  by  corresponding  particles  ;  is  every- 
where capable  of  virtually  unlimited  multiplication, 
without  ever  losing  its  hereditary  endowments ;  is 
often  capable  of  carrying  these  endowments  in  a  dor- 
mant state  through  a  long  series  of  generations,  until 
at  last  they  re-appear  again  in  what  we  recognize  as 
reversions.  Such  being  the  points  of  resemblance,  the 
only  points  of  difference  may  be  summed  up  in  the 
two  words — continuity,  and  stability.  For,  as  regards 
continuity,  while  Darwin's  theory  supposes  the  sub- 
stance of  heredity  to  be  more  or  less  formed  anew  in 
each  generation  by  the  body-tissues  of  that  generation, 


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1 06     An  Examination  of  IVcismannism. 

Wcismann's  theory  rec^ards  tliis  substance  as  owing 
nothing  to  the  body-tissues,  further  than  lodgement 
and  nutrition.  Therefore,  while  the  theory  of  gem- 
mules  can  freely  entertain  the  doctrines  of  Lamarck, 
the  theory  of  ^"-erm-plasm  excludes  them  as  physio- 
logically impossible,  in  all  cases  where  sexual  repro- 
duction is  concerned.  Again,  as  rcgarJs  stability, 
while  Darwin's  theory  simply  accepts  the  fact  of  such 
a  degree  of  stability  appertaining  to  the  substance  of 
heredity  as  the  phenomena  of  atavism.  &c.  prove, 
Wcismann's  theory  postulates  the  stability  of  this 
substance  as  absolute.  But,  as  we  have  now  so  often 
seen,  he  does  so  in  order  to  provide  a  hypothetical 
basis  for  his  further  theory  of  evolution.  In  as  far  as 
his  theory  of  heredity  is  concerned,  there  is  no  reason 
why  it  should  differ  from  Darwin's  in  this  respect. 

Again,  comparing  Wcismann's  theory  of  heredity 
with  that  of  Galton.  we  found  that  germ-plasm 
resembles  stirp  in  all  the  points  wherein  we  have  just 
seen  that  it  resembles  germ-plasm.  Or,  otherwise 
.stated,  all  three  theories  are  thus  far  coincident.  But 
germ-plasm  resembles  stirp  much  more  closel}^  than 
it  docs  gemmules,  seeing  that  the  theory  of  st.rp  is 
founded  on  the  postulate  of  "continuity"  in  exactly 
the  same  manner  as  is  the  theory  of  germ-plasm.  In 
point  of  fact,  the  only  difference  between  these  wo 
theories  consists  in  the  two  further  postulates  presented 
by  the  latter — viz.,  that  the  "continuity"  in  question 
has  been  unbroken  since  the  origin  of  life,  while  the 
"  .stability  "  in  question  has  been  uninterrupted  since 
the  origin  of  sexual  prcpagation.  But  seeing  that 
both  these  additional  postulates  have  reference  to 
Wcismann's  theory  of  evolution,  we  may  say  that  his 


Summary. 


107 


tlicoiy  of  heredity  is.  as  regards  all  essential  points, 
indistinguishable  from  that  of  Galton. 

The  truly  scientific  attitude  of  mind  with  regard  to 
the  problem  of  heredity  is  to  say,  as  Galton  says. 
"  that  wc  might  almost  reserve  our  belief  that  the 
structural  [i.e.,  somatic]  cells  can  react  on  the 
sexual  elements  at  all,  and  we  may  be  confident  that 
at  most  they  do  so  in  a  very  faint  degree ;  in  other 
words,  that  acquired  modifications  are  barely,  if  at 
all,  inJicritcd.  in  the  correct  sense  of  that  word."  But 
for  Weismanns  further  theory  of  evolution,  it  is 
necessary  to  postulate  the  two  additional  doctrines 
in  question  ;  and  it  makes  a  literally  immeasurable 
difference  to  the  theory  of  evolution  whether  or  not 
we  entertain  these  two  additional  postulates.  For  no 
matter  how  faintly  or  how  fitfully  the  substance  of 
heredity  may  be  modi  led  by  somatic  tissues,  by 
external  conditions  ol  life,  or  even  by  so-called 
spontaneous  changes  on  the  part  of  this  substance 
itself,  numberless  causes  of  congenital  variation  are 
thus  admitted,  while  even  the  Lamarckian  principles 
are  hypothetically  allowed  some  degree  of  play.  And 
although  this  is  a  lower  degree  than  Darwin  sui)i)osed, 
their  influence  in  determining  the  course  of  organic 
evolution  may  still  have  been  enormous ;  seeing  that 
their  action  in  any  degree  must  always  have  been 
directive  on  the  one  hand,  and  cuuiulative  on  the 
other. 

Having  thus  pointed  out  the  great  distinction 
between  the  theories  of  stir[)  and  of  germ-plasm, 
it  became  needful  to  note  that  Wcismann  himself 
is  not  consistent  m  observing  i..  On  the  con- 
trary,   in    some    passages    he    apparently   expresses 


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1 08      An  Examination  of  Weismannism, 

himself  as  willinf^  to  resign  both  his  distinctive  postu- 
lates— continuity  ixs  perpetual ^  and  stability  as  absolute. 
But  it  is  evident  that  such  passages  must  be  ignored 
by  his  critics,  because,  although  as  far  as  his  theory 
of  heredity  is  concerned  they  betoken  an  approach  to 
the  less  speculative  views  of  Galton,  any  such  approach 
is  proportionally  destructive  of  his  theory  of  evolution. 
It  must  not  be  supposed  that  I  am  taking  an 
ungenerous  advantage  of  these  ocasionally  funda- 
mental concessions.  On  the  coalrary,  one  cannot  but 
admire  the  candour  which  they  display.  But,  as 
I  have  said,  it  is  necessary  for  us  to  ignore  them,  if 
only  in  order  to  examine  the  VVeismannian  theory  of 
germ-plasm  as  a  distinctive  theory  at  all.  And  more 
than  this.  Seeing  that  his  theory  of  heredity  differs 
from  Galton's  chiefly  in  being  further  an  elaborate 
theory  of  evolution  (founded  on  the  two  additional 
postulates  in  question),  my  main  object  has  been  to 
show  the  enfeeblement  of  the  former  which  Wcis- 
mann  has  caused  by  his  addition  of  the  latter.  If  he 
were  to  express  his  willingness  to  abandon  his  theory 
of  evolution  for  the  sake  of  strengthening  his  theory  of 
heredity  by  identifying  its  main  features  with  those  of 
Galton's,  personally  I  should  have  no  criticism  to  pass. 
Indeed,  I  was  myself  one  of  the  first  evolutionists  who 
called  in  question  the  Lamarckian  factors ;  and  ever 
since  the  publication  of  Galton's  theory  of  heredity  at 
about  the  same  time,  I  have  felt  that  in  regard  to  its 
main  principles — or  those  in  which  it  agrees  with 
Weismann's — it  is  probably  the  true  one.  But  I  can 
nowhere  find  that  Weismann  is  thus  prepared  to 
surrender  his  theory  of  evolution.  Occasionally  he 
plays  fast  and  loose  with  the  two  additional  postulates 


Stuiimary. 


109 


on  which  this  theory  is  founded ;  but  he  docs  so 
without  appearing  to  perceive  the  speculative  im- 
possibility of  any  longer  sustaining  his  temple  of 
evolution  if  he  w^rc  to  remove  its  pillars  of  germ- 
plasm. 

Ignoring,  then,  these  iiiconsistencies,  we  proceeded 
to  examine  separately,  and  on  their  own  respective 
merits,  the  two  distinctive  postulates  of  the  theory 
of  germ-plasm — perpetual  continuity  since  the  first 
origin  of  life,  and  absolute  stability  since  the  first 
origin  of  sexual  propagation. 

It  does  not  appear  to  me  that  very  much  has  to 
be  said,  either  for  or  against  the  former  postulate, 
on  merely  antecedent  grounds,  or  grounds  of  general 
reasoning.  Therefore  I  relegated  to  an  Appendix 
my  examination  of  what  Weismann  has  argued  on 
these  grounds,  while  in  the  text  I  considered  only 
what  he  has  advanced  as  evidence  a  posteriori.  Here, 
as  we  saw,  he  has  developed  three  distinct  lines  of 
verification — viz.  (A)  the  migration  of  germ-cells  in 
some  of  the  Ilydroviedusae,  (1^)  the  early  separation 
of  germ-cells  in  the  ontogeny  of  certain  Invertebrata, 
and  (C)  the  alleged  invariability  of  organisms  which 
are  produced  parthcnogcnetically.  But  we  have  seen, 
with  respect  to  (A),  that  the  specialized  character 
of  germinal  cells  is  a  fact  which  every  theory  of 
heredity  must  more  or  less  recognize  ;  and,  therefore, 
that  the  migration  of  these  cells,  wherever  it  may  be 
found  to  occur,  does  not  lend  any  peculiar  countenance 
to  Weismann's  theory.  There  may  be  many  reasons 
for  such  migratioji  other  than  the  one  which  this 
theory  assigns  ;  while  the  reason  which  it  does  assign 
is  rendered  improbable  by  the  consideration  that  in 


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no     An  Examination  of  Weismannism. 

the  Hydromcdusae  the  material  of  heredity  is  already 
and  richly  diffused  throughout  the  geneal  tissues. 
(B)  and  (C)  arc  both  contrary  to  fact ;  and,  therefore, 
in  whatever  measure  they  would  have  corroborated 
the  theory  had  they  proved  to  be  true,  in  that 
measure  must  they  be  held  to  discountenance  the 
theory  now  that  they  have  been  shown  to  be  false. 

It  appears,  then,  that  there  is  no  evidence  in  support 
of  the  postulate  of  the  perpetual  continuity  of  germ- 
plasm.  There  is  nothing  to  show  the  necessary 
non-inheritance  of  acquired  characters.  The  only 
evidence  which  one  can  recognize  as  good,  is  that  which 
makes  equally  in  favour  of  the  theoiy  of  stirp — or 
rather,  of  the  well-known  fact  that  congenital  charac- 
ters are  at  any  rate  much  viovc  heritable  than  are 
acquired  :  which,  't  is  needless  to  repeat,  is  a  widely 
different  thing  from  proving — or  even  rendering  prob- 
able—  the  absolute  restriction  of  germ -plasm  to 
a  separate  "  sphere  "  of  its  own  "  since  the  origin  of 
life." 

But  now,  although  there  is  no  evidence  in  support 
of  this  postulate,  there  is  no  small  amount  of  evidence 
against  it.  For  this  evidence  goes  to  indicate  that 
no  small  amount  of  reciprocal  action  habitually  takes 
place  between  body-tissues  and  germinal  elements : 
indeed  it  seems  almost  to  prove  that  the  orbits  of 
germ -plasm  and  somato- plasm  are  not  mutually 
exclusive,  but  touch  and  cut  each  other  to  a  con- 
siderable extent.  The  evidence  in  question,  it  will  be 
remembered,  is  derived  from  the  effects  of  puberty, 
enility,  castration,  &c.  ;  the  occasional  effect  of  poUen- 
'zation  on  the  somatic  tissues  of  plants  ;  the  influence 
which  a  stock   occasionally  exercises  upon   a  scion, 


Situiniary. 


1 II 


or  vice  versa,  which  proves  the  possibility  of  a  trans- 
mission of  hereditary  characters  by  a  mere  grafting 
together  of  somatic  tissues  ;  the  direct  evidence  given 
by  De  Vries  that  in  certain  Algae  constituents  of 
cellular  tissue  pass  immediately  from  the  maternal 
ovum  to  the  daughter  organism  ;  and  the  evidence, 
both  direct  and  indirect,  which  remains  to  be  given 
on  a  larger  scale  in  my  subsequent  volume,  where  we 
shall  have  to  challenge  the  validity  of  Weismann's 
fundamental  postulate  touching  the  non- occurrence 
of  Lamarckian   factors  in    any  of  the   multicellular 


organisms. 


It  iDust  here  again  be  noticed  that  in  those  passages 
where  ho  concedes  the  possibly  'occasional"  trans- 
mission of  acquired  characters  Wcismann  is  anni- 
hilating his  own  theory,  root  and  branch.  Thus,  for 
example,  in  allusion  to  De  Vrics'  observation  just 
mentioned,  he  says  that  we  cannot  exclude  the 
possibility  of  "  changes  being  induced  by  external 
conditions  in  the  organism  as  a  whole,  and  then  com- 
municated to  the  germ-cells  after  the  manner  in- 
dicated in  Darwin's  hypothesis  of  pangenesis."  But 
it  is  obvious  that  the  theory  of  germ-plasm  must 
"exclude  the  possibility  of  such  a  transmission  occa- 
sionally occurring '' ;  for  the  very  essence  of  that 
theory  consists  in  its  postulatiiig  a  difference  between 
germ-plasm  and  the  general  body-substance  in  kind, 
such  that  there  never  can  be  anv  '•communication" 
from  the  one  to  the  other  •'  after  the  manner  indicated 
by  Darwin's  hypothesis  of  pangenesis."  Any  pre- 
varication over  this  point  amounts  simply  to  aban- 
doning the  theory  of  germ-plasm  altogether,  and 
opening    up    a    totally    distinct    issue — namely,   the 


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III! 


112     An  Examination  of  Weismannisjn. 

relative  importance  of  natural  selection  and  the 
Lamarckian  factors  in  the  process  of  organic  evolution. 
It  may  be  perfectly  true — and  I  myself  believe  it 
is  perfectly  true — that  Darwin  attributed  too  large 
a  measure  of  importance  to  the  Lamarckian  factors ; 
but  whether  or  not  he  did  so  is  quite  a  different 
question  from  that  which  obtains  between  his  theory 
of  pangenesis  and  VVcismann's  theory  of  germ-plasm. 
The  former  question  is  whether  we  are  to  "  modify " 
the  theory  of  pangenesis,  so  as  to  constitute  it  the 
theory  of  stirp  ;  the  latter  question  is  whether  we  are 
to  "  abolish  "  the  theory  of  pangenesis,  in  favour  of  its 
logical  antithesis,  the  theory  of  germ-plasm.  And 
this  question  remains  to  be  dealt  with  in  my  next 
volume. 

Coming  then,  lastly,  to  the  companion  postulate 
of  germ -plasm  as  absolutely  stable  since  the  first 
origin  of  sexual  propagation,  we  had  to  observe 
that,  unlike  the  one  we  have  just  been  considering, 
there  is  an  immensely  strong  presumption  against  it 
on  merely  antecedent  grounds.  That  the  most  com- 
plex substance  in  nature  should  likewise  be  the  most 
stable  substance  with  regard  to  complexity  of  "  mole- 
cular structure " ;  that  the  greater  its  complexity 
becomes  the  greater  becomes  its  stability,  so  that 
while  in  the  comparatively  simple  unicellular  organ- 
isms it  is  eminently  susceptible  of  modification  by 
external  conditions,  it  entirely  ceases  to  be  thus 
susceptible  when  it  becomes  evolved  into  the  incom- 
parably more  complex  and  immensely  more  varied 
structures  which  form  the  bases  of  heredity  in  the 
multicellular  organisms — where,  also,  it   must  come 


Siunmary. 


113 


into  ever  more  and  more  intricate  as  well  as  more  and 
more  diverse  relations  with  the  external  world  ;  — all 
this  is,  I  repeat,  well  niijjh  incredible.  At  any  rate, 
speaking  for  myself,  I  should  require  some  enormous 
weight  of  evidence  to  balance  so  enormous  an  ante- 
cedent improbability,  or  before  I  could  reL;ard  such 
a  doctrine  as  meriting  any  serious  attention. 

What,  then,  is  the  evidence  that  has  been  adduced  ? 
We  have  found  that  this  evidence  is  ;///.  On  the 
other  hand,  we  have  found  that  the  evidence  against 
the  doctrine  is  abundantly  sufficient  to  annihilate  the 
doctrine — and  this  cjuitc  apart  from  all  the  antecedent 
considerations  just  alluded  to.  Vox  not  only  have  we 
the  sundry  facts  of  bud-variation,  a-sexual  origin  of 
species,  &c.,  which  contradict  the  doctrine  ;  but  we 
have  also  the  results  of  direct  experiment,  which 
prove  that  the  all(;gcd  stability  of  germ-plasm  may  be 
conspicuously  upset  by  slight  changes  in  the  external 
conditions  of  life.  So  that  both  from  within  and  from 
without  the  stability  which  is  alleged  in  theory  admits 
of  being  overturned  by  facts. 

And  here,  in  order  to  avoid  all  possible  confusion, 
I  must  ask  it  once  more  to  be  noted  that  there  is  not, 
and  never  has  been,  any  question  touching  the  hii^h 
degree  of  stability  which  is  exhibited  by  whatever 
substance  it  is  that  constitutes  the  material  basis  of 
heredity.  Ikit  this  is  a  widely  different  thing  from 
supposing  the  stability  absolute,  so  that  it  can  never 
have  been  affected  in  any  degree  since  the  first  origin 
of  multicellular  organisms,  or  in  any  of  the  millions  of 
species  into  which  these  organisms  have  ramified. 
And  the  fact  that  in  some  cases  we  are  actually 
able  to  observe  a  change  of  congenital  characters  as 


F?'. 


nr 


ll 


114    An  Exam ituit ion  of  Wcismannisni. 

resulting  from  some  "  spontaneous "  chaiv^x'  in  the 
hereditary  material  itself  (as  in  bud-variation),  or  from 
some  chani^^e  in  the  external  conditions  of  life  (as  in 
Hoffmann's  experiments) — this  fact  is  more  than  is 
required  in  order  finally  to  overthrow  the  intrinsically 
untenable  doctrine  which  is  in  question. 

Now,  with  the  collapse  of  this  doctrine  there 
collai)ses  also  the  important  chain  of  deductions 
therefrom,  which  together  constitute  Weismann's  new 
theory  of  evolution.  In  particular,  that  natural  selec- 
tion is  the  exclusive  means  of  modification  among  all 
the  Metazoa  and  Metaphyta,  while  it  is  as  exclusively 
ruled  out  with  respect  to  all  the  Protozoa  and  Pro- 
tophyta  ;  that  individual  variations  among  the  former 
can  only  be  determined  by  sexual  unions,  while  among 
the  latter  they  can  only  be  determined  by  the  direct 
action  of  the  environment  ;  that  the  origin  of  con- 
genital variability  in  all  the  Metazoa  and  Metaphyta 
is  to  be  sought,  and  can  only  be  found,  in  variations 
which  occurred  millions  of  years  ago  in  the  Protozoa 
and  Protophyta ;  that  the  "  significance  of  sexual 
propagation  "  is  to  be  found  in  the  view,  that  by  this 
means  alone  can  congenital  variations  have  been  ever 
since  produced  ;  &c.,  &c. 

Upon  the  whole  then,  it  appears  to  me  that  both 
the  fundamental  postulates  of  the  theory  of  germ- 
plasm  are  unsound.  That  the  substance  of  heredity 
is  largely  continuous  and  highly  stable  I  see  many 
and  coeent  reasons  for  believing.  But  that  this  sub- 
stance  has  been  uninterruptedly  continuous  since  the 
origin  of  life,  and  absolutely  stable  since  the  origin 
of   sexual  propagation,  I  see  even  more  and  better 


Shin  ma  I 


y 


H5 


reasons  for  cHsl)clicvi^L,^  And  inasmuch  as  these  two 
latter,  or  distinctive,  postulates  are  not  nceiled  for 
Weisniaiuis  theory  of  hercdit)',  while  they  are  both 
essential  to  his  theory  of  evolulinii,  I  cannot  but 
rcifret  that  he  sh(nild  thus  have  crii)i)lcd  the  former 
by  burdeninf:^  it  with  the  latter.  Hence  my  object 
throuL^hout  has  been  to  (lisj)lay,  as  shar[)l\'  as  possible, 
the  contrast  that  is  presented  bctuern  the  brass 
and  the  clay  in  the  colossal  fiLjure  which  Weismann 
has  constructed.  Hence,  also,  my  emphatic  dissent 
from  his  theory  of  evolution  does  not  prevent  me 
from  sincerely  a[)preciatin<;  the  L;reat  value  which 
attaches  to  his  theory  of  heredity.  And  althoui;h  I  have 
not  hesitated  to  say  that  this  theory  is,  in  my  opinion, 
incomplete;  that  it  presents  not  a  few  manifest 
inconsistencies,  and  even  logical  contradictions;  that 
the  facts  on  which  it  is  foiuided  have  always  been  facts 
of  general  knowledi;e ;  that  in  all  its  main  features  it 
was  present  to  the  mind  of  Darwin,  and  distinctly 
formulated  by  Galton  ;  that  in  so  far  as  it  has  been 
constituted  the  basis  of  a  more  general  the  ry  of 
organic  evolution,  it  has  clearly  proved  a  failure  : — 
such  considerations  in  no  wise  diminish  my  cordial 
recognition  of  the  services  which  its  distinguished 
author  has  rendered  to  science  by  his  speculations 
upon  these  topics.  For  not  onl)'  has  he  been  suc- 
cessful in  drawing  renewed  and  much  more  general 
attention  to  the  important  questions  touching  the 
transmissibility  of  ac(iuired  characters,  the  causes  of 
variation,  and  so  on  ;  but  e\  en  those  parts  of  his 
system  which  have  proved  untenable  are  not  without 
such  value  as  tem[)orary  scatloldings  present  in  re- 
lation to  permanent  buildings.     Therefore,  if  I  have 


!if 


;f  j 


!  ii\ 


'j  3  i. 

Hi 


1 1 


■  i 

!    1 


I  2 


pp 


111 


I  16    Aji  /examination  of  IVcismannism. 

appeared  to  play  the  rdlc  of  a  hostile  critic,  this  has 
only  been  an  exjjression  of  my  desire  to  separate 
what  seems  to  me  the  ^nain  of  ^ood  science  from  the 
chaff  of  bad  speculation.  And  the  candour  which 
Professor  VVeismann  has  always  displaj-ed  towards 
criticism  of  this  character  enables  nie  to  hope  with 
assurance,  that  I  have  said  nt  thinij  which  he  him- 
self will  re<;ard  as  inconsistent  with  high  admiration 
of  his  work  as  a  naturalist,  or  of  his  orij^inality  as 
a  philosopher. 


CllAl'lliR  V. 


Hi 

m 


Whismannis.m  ui'  to  datk  (1H93). 

Hitherto  wc  have  been  consldciintr  rrofossor 
Wcisniann's  system  as  it  stood  prior  to  the  publica- 
tion of  his  most  recent  works  on  Ai)ipJiiuiixis  and  TItc 
Germ-plasm,  in  i  (S(^.  1  and  1  (Sy^  resi)ectively.  These 
later  and  hii^hly  elaborate  essays  present  considerable 
modifications  of  the  system,  as  it  stood  when  the 
forej;f)ing  criticism  was  written.  lint,  for  reasons 
already  stated  in  the  Preface,  it  ajjpears  to  me 
desirable  to  leave  that  criticism  as  it  was  -"risj^inally 
constructed,  and  to  su[)ply  this  further  chapter  for 
the  purpose  of  dcalini^  with  the  large  alterations  of, 
and  important  additions  to,  the  theory  of  germ-plasm, 
which  the  maturer  thought  of  its  gifted  author  has  led 
him  to  announce. 

A  few  general  remarks  may  be  most  conveniently 
made  at  the  outset. 

In  the  first  place,  these  recent  publications  present 
the  advantage  over  their  predecessors  of  being  sys- 
tematic treatises,  instead  of  more  or  less  independent 
papers.  On  this  account  they  present  a  logical 
sequence  of  thought,  which  renders  the  task  of  ex- 
amination much  less  difficult  than  it  was  in  the  case 
of  the  first  volume  of  the  Essays. 


R'^l 


ifi  MH 


'ill!   ■! 


ii8    A7t  Examinatio7i  of  Wcisviannism. 

In  the  second  place,  as  a  result  of  hts  more  matured 
reflection,  Professor  Wcismann  lias  himself  perceived 
a  considerable  number  of  the  difficulties  and  objections 
which  I  have  set  forth  in  the  precedinc^  chapters. 
And  not  only  has  he  thus  anticipated  many  of  my 
criticisms  ;  but.  as  a  result  of  doing  so,  he  has  changed 
not  a  few  of  the  most  important  parts  of  his  previous 
system,  with  the  result  of  greatly  improving  it. 

But,  in  the  third  place,  notwith.standing  that  his 
remarkable  power  of  .speculative  thinking  is  every- 
where united  with  adequate  knowledge  in  the  sundry 
branches  of  biological  science  with  which  it  deals, 
I  confess  to  a  serious  doubt  whether  it  has  not  been 
permitted  to  enjoy  an  undue  amount  of  liberty.  If 
only  they  can  be  laced  together  by  a  thread  of  logical 
connexion,  hypotheses  are  added  to  hypotheses  in 
such  profusion  as  we  are  acquainted  with  in  the  works 
of  metaphysicians,  but  w'hich  has  rarely  been  ap- 
proached in  those  of  naturalists.  The  whole  mechanism 
of  heredity  has  been  now  planned  out  in  such  minute- 
ness of  detail  and  assurance  of  accuracy,  that  in  reading 
the  account  one  is  reminded  of  that  which  is  ijiven 
by  Dante  of  the  topography  of  Inferno.  For  not 
only  is  the  "  sphere  "  of  germ-plasm  now  composed 
of  nine  circles  (molecules,  biophores,  determinants,  ids, 
idants,  idio-plasm,  somatic-idioplasm,  morpho-plasm, 
apical-plasm),  but  in  most  of  these  regions  our  guide 
is  able  to  show  us  such  strange  and  interesting  phe- 
nomena, that  we  return  to  the  fields  of  science  with 
a  sense  of  hav'ng  been  indeed  in  some  other  world. 
Or,  to  change  the  metaphor,  if  it  be  the  case  that 
'"a  true  scientific  judgement  consi.sts  in  giving  a  free 
rein    to   speculation   with    one    hand,    while    holding 


IVeisiuaiinisvi  up  to  date  (1893).        119 


ready  the  break  of  verification  with  the  other,"  I  think 
it  must  be  admitted  that,  in  as  far  as  he  has  erred. 
Professor  Wcismann  has  done  so  by  driving  a  chariot 
which  is  unprovided  with  any  break  at  all. 

Hence,  fourthly,  it  is  needless  to  follow,  even  in 
epitome,  the  innumerable  windings  of  these  never- 
ending  speculations.  For,  on  the  one  hand,  it  would 
be  impossible  to  do  so  without  adding  an  unduly 
extended  chapter  to  our  already  tediously  prolonged 
consideration  of  Wcismann's  views ;  while,  on  the 
other  hand,  we  should  have  to  deal  merely  with  matters 
of  comparative  detail.  The  additions  which  have 
been  made  to  his  theory  by  his  most  recent  publica- 
tions are  chiefly  concerned  with  the  matter  just 
alluded  to — viz.,  a  minute  (elaboration  of  the  hypo- 
thetical mechanism  of  heredity,  in  accordance  with 
the  general  theory  of  germ- plasm.  Without  question 
this  elaboration  is  everywhere  thoughtful,  and  often 
highly  ingenious ;  but  until  the  general  theory  in 
question  shall  have  been  satisfactorily  grounded,  it 
seems  premature  to  supply  so  immense  a  design  of 
purely  deductive  construction,  l^eautiful  though  it 
may  be  in  its  imposing  elevation,  this  drawit'^g  of 'the 
architecture  of  germ-plasm "  must  be  regarded  as 
a  work  of  artistic  imagination  rather  than  as  one  of 
scientific  generalization.  Frcm  the  latter  ponit  of 
view  it  is  at  most  a  temple  ///  fosse,  and  even  if  it  is 
ever  to  be  realized  ///  esse,  we  cannot  allow  the  actual 
building  to  begin  until  we  are  much  more  sure  than 
anybody  is  at  present  entitled  to  be  touching  the 
foundations  <  .,  hich  it  is  pro^iosed  to  rear  so  great 
an  edifice. 

Again,  and  fifthly,  even  if  Weismann  should  ever  be 


1^ 


III 


1 20    An  Examination  of  Weismannism. 

able  to  satisfy  us  upon  this  matter,  or  fully  to  demon- 
strate his  basal  proposition  touching  the  perpetual 
continuity  of  i]jerm-plasm,  there  would  still  be  a  far  cry 
between  accepting  this  sufficiently  simple  proposition 
and  supposing  that  there  is  any  adequate  reason  for 
entertaining  so  comi)lcx  a  scheme  of  the  structure  of 
germ-plasm.  No  doubt  Weismann  himself  would  be 
quite  ready  to  admit,  that  from  his  basal  proposition 
of  the  continuity  of  germ-plasm  it  is  logically  possible 
to  construct  many  other  designs  of  the  architecture  of 
germ-plasm,  besides  the  one  which  he  has  so  beautifully 
drawn.  And  although  most  of  such  alternative  designs 
would  doubtless  embody  some  one  or  other  of  the 
features  which  are  presented  by  his  own,  no  one  could 
say  which  features  common  to  any  two  of  the  designs 
represent  the  facts.  For  in  the  case  of  all  alike 
there  would  be  a  necessary  absence  of  verification : 
the  architects  would  all  and  etiually  have  to  ac- 
knowledge that  their  imposing  pictures  of  "the  palace 
of  truth  "  were  but  imai;inary.  S^h,  in  my  opinion, 
has  been  the  case  with  all  theories  of  the  ultimate 
mechanism  of  heredity  hitherto  published  ;  but  the 
difference  between  them  and  Weismann's  theory  in 
this  respect  is,  that  while  most  of  the  others  have  not 
f;one  into  speculative  details  further  than  was  necessary 
as  a  means  of  substantiating  their  basal  postulates, 
Weismann's,  as  now  developed  in  TJic  Gcrvi-plasvi,  is 
mainly  concerned  with  .such  .speculative  details  as  aa 
end,  or  object  per  se. 

l^ut,  it  may  be  replied,  by  thus  constructing  an 
ideal  mechanism  of  heredity  Weismann  is  greatly 
strengthening  his  fundamental  postulate  of  the  con- 
tinuity of  germ-plasm,  becau.se  he  shows  how  all  the 


I 


cmon- 
petual 
far  cry 
osition 
jon  for 
ture  of 
uld  be 
losition 
lossible 
;ture  of 
utifuUy 
designs 
of  the 
e  could 
dcsifj^ns 
11   alike 
1  cat  ion : 
to    ac- 
palacc 
Dinicm, 
timatc 
but  the 
eory  in 
avc  not 
cessary 
tulates, 
Idsvi,  is 
s  as  an 

ting  an 
greatly 

ic  con- 
all  the 


Wcisnmttiiism  up  to  date  (1S93).       121 

main  facts  of  heredity,  and  allied  phenomena,  admit 
of  being  explained  if  once  the  postulate  be  accepted. 
If  this  were  urged,  however,  I  should  have  two  remarks 
to  offer.  The  first  is  that  VVeismann,  in  constructing 
his  ideal  mechanism,  has  gone  very  much  further  in 
the  way  of  elaboration  than  can  possibly  be  required 
for  this  purpose.  So  much  further,  indeed,  that  his 
purpose  has  evidently  been  the  constructing  of  his 
ideal  mechanism,  as  I  have  just  said,  for  its  own  sake, 
and  not  for  the  sake  of  substantiating  its  basal  pro- 
position by  showing  how  well  the  latter  can  be  made 
to  wot';  in  explaining  the  phenomena  of  heredity,  &c. 
Mor;.:;;  * — and  this  is  my  second  remark — however 
wc.'i  ihe  basal  proposition  may  be  made  to  work  in 
this  respect,  we  must  not  be  deceived  into  supposing 
that  such  a  fact  is  equivalent  to  a  substantiation  of 
the  proposition.  This  proposition — the  continuity  of 
germ-plasm — is  the  inverse  of  that  which  constitutes 
the  basis  of  the  theory  of  pangenesis.  Voy  while  the 
latter  assumes  that  in  the  last  resort  it  is  always 
somatic  tissues  which  produce  the  substance  of 
heredity,  the  forn^cr  simply  inverts  the  terms  of  this 
assunrption,  ar  J  liolds  that  it  is  always  the  substance 
of  heredity  w;,j:h  ^roduces  the  somatic  tissues.  Now, 
in  all  cases  ,vV  *%;  me  theory  consists  in  thus  simply 
inverting  the  t^i  ^'s  uf  another,  it  will  be  found  that 
the  facts  which  ihey  both  seek  to  ex[)lain  lend 
themselves  equally  to  explanation  by  either,  up  to 
some  certain  and  usually  distant  point,  where  a  crucial 
test  becomes  possible.  Take,  as  an  example,  the 
geocentric  ind  heliocentric  theories  of  the  solar 
system.  I  -c  the  question  was  whether  the  earth 
moved  rou-      -A  ^  .sun,  or  vice  versa  \  and  so  many  of 


m 


•^ 


i:  I 


lis 


122    ^«  Examination  of  Weismannis^n. 

the  facts  of  observation  lent  themselves  equally  well 
to  either  interpretation,  that  it  was  very  many  centuries 
before  the  crucial  tests  were  forthcoming.  So,  in  the 
present  instance,  the  question  is  as  to  whether  the 
carriers  of  heredity  move  from  body-cells  to  germ- 
cells,  or  vice  versa ;  and  it  is  because  the  theory 
which  sustains  the  latter  view  has  merely  to  invert 
the  terms  of  the  one  which  takes  the  former,  that  so 
many  of  the  facts  of  observation  lend  themselves 
equally  well  to  both — a'-  ve  have  seen  in  chapter  III 

(pp.  56-59)- 

Lastly,  yet  another  rea.s       ♦or  not  considering  in 

any  detail  Professor  Wcismanns  intricate  speculations 

on  the  ultimate  mechanism  of  heredity  is,  that  by  so 

doing  I    should   have   found   it   impossible  to    avoid 

obscuring  the  main  issues.     For  even  Professor  Weis- 

mann    himself,  by  the   extreme  care   which    he    has 

taken  in  fully  presenting  his  scheme  of  this  ultimate 

mechanism,    has    not    found    it    practicable   to    keep 

distinctly  before  our  view  the  relative  insignificance 

of  such    details,  as  conii)ared   with  the  fundamental 

importance  of  his  original  postulates.     Hence,  I  have 

deemed  it  best  in  the  present  chapter  to  restrict  our 

attention  to  the  changes  which  he  has  recently  made 

in  these  the  foundations  of  his  entire  system. 

For  these  reasons,  then,  I  will  mention  only  those 

main  features  in   the  '•  architecture  of  germ-plasm  " 

which  it  is  necessary  to  understand  for  the  purposes  of 

the  following  criticism  touching  the  general  theory  of 

germ-plasm  in  the  most  recent  phase  of  its  evolution. 

To  begin  with,  Wcismann  has  now  seen  the  desira- 
bility of  ceasing  to  designate  the  ultimate  ''carriers  of 


" 


m 


Weis7fiaitn7sni  itp  to  date  (1893).       123 

heredity"  by  the  term  "molecules."  Indeed,  in  these 
later  volumes  he  has  fully  anticipated  my  remarks 
touching  the  use  of  this  term  in  his  previous  "  Ussays  ^" 
The  result  of  his  more  mature  reflection  may  be 
presented  in  epitome  thus. 

A  number  of  "  molecules,"  in  the  proper  or  chemical 
sense  of  the  word,  go  to  form  a  "  biophore,''  which  is 
the  ultimate  unit  of  living  substance. 

A  number  of  "  biophores "  go  to  form  a  "deter- 
minant," which  is  a  special  element  in  the  germ-plasm, 
capable  of  directing  the  ontogeny  of  such  and  such 
a  group  of  cells  as  is  independently  variable  from  the 
germ  onwards. 

A  number  of  "determinants  "  go  to  form  an  "id," 
which  is  the  same  hypothetical  body  as  Weismann 
has  hitherto  designated  by  the  term  "  ancestral  germ- 
plasm."  That  is  to  say,  it  is  a  group  of  determinants 
indissolubly  united  in  phylogeny,  and  therefore 
transmitted  by  heredity  as  one  complex  whole.  Ids 
are,  perhaps,  microscopically  visible  ;  and,  if  so,  they 
probably  correspond  to  the  small  granules  (micro- 
somata),  which  are  familiar  to  the  histologist  in  the 
structure  of  chromosomes. 

A  number  of  "  ids  "  go  to  form  an  "  idant,"  which 
is  a  chromosome,  or  chromatin  fibre-. 

In  my  opinion  the  most  important  advance  which 
Weismann  has  made  in  his  theory  by  means  of  this 
scheme  has  reference  to  the  third  of  these  divisions — 
the  determinant.  It  is  a  matter  of  observation  that 
every  cell  of  a  multicelluar  organism  does  not  vary 


*  See  aliovo,  p.  -.j^,  note, 

*  Sec  /><iru'iii  (iii.i  (t//er  Ihinvin,  Pnrt  T,  p.  129. 


'  tf  ff 


m 


m    l\\ 


1 24    Afi  Examination  of  Wcisviannism, 

independently :  it  appears  to  be  always  the  case  that 
in  the  phenomena  of  variation  a  smaller  or  a  larger 
group  of  cells  is  concerned.  Now  there  must  be 
something  that  determines  the  similar  and  simul- 
taneous variation  of  such  a  whole  group  of  cells; 
and,  in  all  cases  where  such  a  variation  is  congenital, 
it  is  certain  that  this  something  must  be  contained 
in  the  substance  of  heredity.  So  far,  I  think,  we 
must  all  agree,  whether  or  not  we  regard  this  sub- 
stance as  "germ-plasm,"  In  other  words,  whether 
we  regard  the  carriers  of  heredity  as  proceeding 
ccntrifugally  (germ-plasm)  or  centripetal ly  (gemmules), 
it  seems  to  me  that  we  ought  to  accept  Weismann's 
doctrine  of  determinants.  Indeed,  pathologists  have 
already  furnished  a  foreshadowing  of  such  a  doctrine 
in  regard  to  the  phenomena  presented  by  certain 
diseases,  such  as  cancer  ;  but  it  is  an  important  step 
to  have  extended  the  idea  from  pathology  to  biology 
in  general — and,  at  the  same  time,  to  have  given  it 
a  more  definite  shape  than  it  has  hitherto  presented. 
In  Weismann's  hands  it  serves  to  render  more  con- 
ceivable— if  not  also  more  intelligible — that  process 
of  marshalling  cell-formations,  which,  be  our  theories 
what  they  may,  is  assuredly  the  most  distinctive  and 
remarkable  fact  of  ontogenetic  organization. 

Again,  as  regards  the  id,  I  do  not  sec  how  any  one 
can  attentively  read  Professor  Weismann's  discussion 
without  acknowledging  that,  if  we  once  accept  his 
doctrine  of  determinants,  his  sequent  doctrine  of  ids 
becomes  a  logical  necessity. 

On  the  other  hand,  however,  I  do  not  see  that 
such  is  the  case  with  respect  to  idants  ,  and  still  less 
do  I   see  any  reason  for  identifying  the  latter  with 


IVeismannism  tip  to  date  (1893).        125 

chromosomes — even  assumincj  that  chromosomes  arc 
the  visible  repositories  of  the  carriers  of  heredity  ^ 

Referring  the  reader  to  Weismann's  own  exposition 
for  a  full  account  of  these  and  many  othert  additions 
to  his  general  theory  of  germ-plasm,  I  will  at  once 
proceed  to  consider  the  alterations  or  emendations  of 
that  theory  which  have  been  published  in  his  last  two 
volumes,  and  which,  as  we  shall  find,  have  in  large 
measure  anticipated  some  of  the  most  important  points 
in  the  foicijoing  criticism.  Therefore  in  the  foUowincr 
criticism  I  will  consi^'er  seriatim  what  he  has  now  said 
touching  all  these  points,  and  conclude  by  offering 
some  general  remarks  on  the  resulting  position  of  his 
general  system  of  theories  up  to  the  present  date. 

Pursuing  the  same  method  of  criticism  as  that 
adopted  in  the  preceding  chapters,  we  will  first  con- 
sider the  further  modifications  of  Weismann's  theory 
of  heredity,  and  next  those  of  his  theory  of  organic 
evolution. 


WcisDiann's  theory  of  Heredity  ( 1  Hy^^). 

First  of  all,  Weismann  has  now  profoundly  modified 
his  theory  of  polar  bodies.  For,  owing  to  certain 
more  recent  researches  of  Professor  O.  Ilertwig.  he 
very  candidly  allows  : — "•  My  previous  interpretation 
of  the  first  polar  body  as  the  removal  of  ovogenetic 
nucleo-plasm  from  the  egg  must  fall  to  the  ground : 
about  this  there  is  no  possible  duubt  -." 

*  It  must  always  l)e  renieml)crcil  tliat  the  view  ndoiited  by  Wcismmin 
touchiii_^'  the  mieleus  i,niul  more  especiall)  the  chroiiHisomes)  of  a  i;erin- 
cell  beiny;  tlie  sole  seat  ui  heieilily,  is  still  tar  Imin  havinj;  hecii  estal> 
lished. 

'•*  Essays,  vol.  ii.  p.  122. 


"W 


i   : 


ill 


I 


i< 


' 


i;  : 


126    An  Exauiiiiation  of  Wcisinannisiu. 

He  now  rej^^ards  both  pol.ir  bodies  as  concerned  in 
the  same  function  of  removinij  supcrnuous  germ-plasm. 
Tiiereforeone-half  of  his  previous  theory  is  abandoned  : 
"  the  ovoL;enetic  idio-plasm "  is  now  supposed  to  be 
simply  absorbed  in  the  couise  of  ontot^eny,  as  I  had 
suLj^t^ested  in  one  of  the  precedin<^  chapters  (pp.  42-46). 
Tile  consequence  is  that  he  has  now  nothini^  to  oppose 
to  the  view  which  is  likewise  there  sui;-gested  (pp.  43- 
44)— viz.,  that  his  whole  theory  of  polar  bodies  is 
rendered  needless  and  improbable  by  the  fact  that  the 
very  mode  in  which  ova  are  produced  renders  ample 
provision  for  the  removal  of  any  amount  of  superfluous 
i:jerm-plasm  which  the  theory  of  germ-plasm  may 
require. 

It  is  needless  to  say.  after  what  '  as  already  been 
said  in  the  pages  just  referred  to,  that  in  my  opinion 
Professor  Weismann  has  improved  his  main  system 
of  theories  by  dropping  this  part  of  his  subordinate 
and,  for  the  most  part,  separate  theory  of  polar  bodies. 
I  only  wi  h  he  could  have  seen  his  way  to  dropping 
the  whole. 

Again,  he  has  now  fully  considered  the  phenomena 
of  repair.  regeneraticMi,  reproduction  from  somatic 
tissues,  budding,  and  graft-hybridi/.ation. 

Touching  the  four  former  he  takes  the  view  which 
I  have  supposed  that  he  would  (p.  53).  As  regards  the 
latter,  he  fully  accepts  the  fact  of  an  occasional  trans- 
mission of  characters  from  one  species  or  variety  of 
plant  to  another  by  mere  grafting  ^  But.  although  the 
explanation  which  he  gives  of  this  fact  may  pass 
muster  so  far  as  the  only  case  which  he  deals  with  in 

'    The  iio/n  Jltisiit,  p.  342. 


ri 


IVeisJUiHiiiisni  up  to  date  (1893).        127 

detail  is  concerned.  I  do  not  see  how  it  can  tlo  so 
to  many  others.  l*\)r  tlie  case  which  he  considers  is 
that  of  Cystisus  adaDii,  where  a  bud  of  one  species 
of  Laburnum  having  been  inserted  in  the  wood  of 
another  produced  a  shoot  which  prcsiMited  inter- 
mediate characters  ;  and  these  have  ever  since  been 
propai;ated  by  cuttint^s.  Weismann's  interpretation  of 
the  facts  here  is,  "  that  they  were  due  to  an  abnormal 
kind  of  amphimixis,  so  that  the  idants  of  both  si)ecies 
were  combined  in  the  apical  cell  of  the  first  shoot  '." 
Now,  although  this  explanation  may  well  apply  to 
a  case  of  graft-hybridization  by  means  of  buds,  it 
obviously  cannot  do  so  to  any  case  where  hybridization 
is  produced  by  the  grafting  of  woody  tissues.  For 
here  there  is  no  "  apical  cell  "  in  the  question  ;  and 
therefore  the  difficulties  which  I  have  adduced  on 
page  82  remain.  Possibly  Wcismann  may  dispute 
the  fact  of  hybridization  in  any  of  these  cases  ;  but, 
as  he  has  not  expressly  done  so,  I  will  not  go  into 
the  question  of  evidence  ^. 


One  important  addition  to  this  side  of  Weis- 
mann's system  has  been  made  in  order  to  meet 
the  class  of  difficulties  which  are  presented  by  the 
apparent  inheritance  of  certain  climatic  variations,  as 
already  mentioned  on  pp.  67-(S.  For  example,  his 
own  butterflies  seemed  to  render  definite  proof  of 
somatogenetic  variations  c:iused  by  changed  con- 
ditions of  life  being  transmitted  to  progeny.  There- 
fore, it  will  be  remembered.  Wcismann  candidly 
admitted,  "  even  now  I  cannot  explain  the  facts 
otherwise  than  by  supposing  a  passive  accjuisition  of 

'  TJu  GcriH-plasm,  p.  342.  ^  Sec,  however,  j).  83,  note. 


11'  -itT^ 


P  ! 


i  i 


128    An  Examination  of  Weismannism. 

characters  produced  by  the  direct  influence  of 
ch'mate" — i.e.,  an  exactly  representative  copyin<T  in 
progeny  of  characters  acquired  by  parents.  I  have 
already  quoted  these  words  in  order  to  show  their 
logical  inadmissibility  as  used  by  Weismann.  He 
cannot  be  allowed  thus  to  entertain  the  Lamarckian 
factors  and  at  the  same  time  to  maintain  his  theory 
of  germ-plasm,  which  excludes  them  as  physiologically 
impossible.  Doubtless  he  was  himself  aware  of  this, 
for  he  immediately  added  that  "  new  experiments  will 
be  necessary  to  afford  the  true  explanation  ^" 

The  explanation,  however,  which  he  now  gives  is 
not  based  on  any  new  experiments,  but  on  a  new 
suggestion  to  the  effect  that  all  such  seemingly 
conclusive  instances  of  the  inheritance  of  acquired 
characters  are,  in  truth,  illusory.  This  suggestion  is 
that  "  Many  climatic  variations  may  be  due  wholly 
or  in  part  to  the  simultaneous  variation  of  corre- 
sponding determinants  in  some  parts  of  the  soma,  and 
in  the  germ-plasm  of  the  reproductive  cells,-"  For 
example,  if,  as  Weismann  now  supposes,  determinants 
of  the  same  kinds  occur  in  the  somatic  tissues  as  well 
as  in  the  germ-cells,  when  a  particular  spot  occurs  on 
a  butterfly's  wing,  it  has  been  due  to  a  particular  kind 
of  determinant  which  in  the  course  of  ontogeny  was 
transmitted  from  the  germ-cell  for  the  express  purpose 
of  controlling  the  size  and  colour  of  the  spot.  But 
a  residue  of  precisely  similar  determinants  was  re- 
served in  the  germ-cell  (germ-plasm),  for  the  purpose 
of  determining  a  precisely  similar  spot  in  the  next 
generation.  Hence,  if  a  rise  of  temperattjre,  or  any 
other  external  change,  is  capable  of  so  acting  on  the 

'  Essays,  vol.  i  p.  101.  Italics  mine.         *   'J'kc  Germ-plasm,  p.  406. 


Weis))iaiinis)ii  np  to  date  (1893).        129 


:nce    of 
►ying   in 
I  have 
ow  their 
nn.     He 
narckian 
is  theory 
.logically 
e  of  this, 
-lents  will 

^  gives  is 
Dn  a  new 
seemingly 
■  acquired 
fTcstion  is 
|ue  wholly 
of  corre- 
soma,  and 
s.-"     For 
;erminants 
les  as  well 
occurs  on 
cular  kind 
Dgcny  was 
ss  purpose 
pot.     But 
was  re- 
le  purpose 
the  next 
re,  or  any 
ng  on  the 

asm,  1'.  406' 


determinant  in  the  soma  as  to  cause  it  to  impart  an 
abnormal  colour  to  the  spot  when  formed,  a  similar 
change  is  likely  to  be  simultaneously  effected  in  the 
corresponding  determinants  which  arc  lying  dormant 
in  the  germ-plasm.  Therefore,  when  the  latter  become 
active  in  the  ontogeny  of  the  next  generation,  they 
will  produce  spots  presenting  the  same  variations  as 
those  of  the  i)rcccding  generation.  Obviously,  how- 
ever, there  would  not  be  here  any  transmission  of 
acquiretl  characters.  The  change  would  be  "  special- 
ized," but  not  '•  representative." 

No  doubt  we  have  here  a  sufficiently  ingenious 
method  of  circumventing  an  awkward  class  of  facts. 
But  I  should  like  to  make  two  observations  with 
regard  to  it. 

In  the  first  place,  the  suggestion  is  highly  specu- 
lative, and  has  been  advanced  solelv  for  the  sake  of 
saving  the  theory  of  germ-plasm.  There  are  no  facts 
adduced  in  its  favour,  and  it  could  scarcely  be  enter- 
tained as  in  the  least  degree  probable  by  any  one 
who  has  not  already  accepted  the  theory  in  question. 
Hence,  unless  we  are  to  embark  on  a  course  of 
circular  reasoning,  we  must  refuse  to  accept  the 
explanation  of  hereditary  climatic  variation  now 
offered,  until  it  shall  have  been  fully  corroborated  by 
the  experimental  enquiry  to  which  Weismann  says  he 
is  now  submitting  it. 

My  second  observation  is.  that  the  suggestion  is 
not  new ;  but  appears  to  have  been  derived  from 
Professor  Weismann's  recent  study  of  Mr.  Galton's 
Theory  of  Heredity.  At  all  events,  the  suggestion  is 
there  presented  with  sufficient  lucidity,  thus:  — 
It  is  said  that  the  structure  uf  an  animal  changes  when  he  is 

K 


..J*  •  I'jl 


J    i 


\i  U 


i^^o    An  Examination  of  Weisniannism. 

placed  under  changed  conditions ;  that  his  <ifTspring  inherit  some 
of  his  change  ;  and  that  tliey  vary  still  luriher  on  their  own  ac- 
count, in  the  same  direction,  and  so  on  through  successive  genera- 
tions, until  a  notable  change  in  the  congenital  characteristics  of  the 
race  has  heen  efiected.  Hence,  it  is  concluded  that  a  change 
in  the  personal  structure  has  reacted  .m  the  sexual  elements. 
For  my  part,  1  object  to  so  general  a  conclusion,  for  the  fol- 
lowing reason3.  It  is  universally  ailmitted  that  the  primary 
agents  in  the  processes  (S  growth,  nutrition,  and  reproduction 
are  the  same,  and  that  a  true  theory  of  heredity  must  so  regard 
them.  In  other  words,  the)-  are  all  due  to  the  development 
of  some  germinal  maticr,  variously  located.  Conseciuently,  when 
similar  gcri-n.inal  matter  is  everywhere  affected  by  the  same 
condilif/ns,  we  should  expect  that  it  would  be  everywhere 
affected  in  the  same  way.  The  particular  knid  of  germ  whence 
the  hair  sprang,  that*  was  induced  to  throw  out  a  new  variety 
in  the  cells  nearest  to  the  surface  of  the  body  under  certain 
changed  conditions  of  climate  and  food,  might  be  expected  to 
throw  out  a  similar  variety  in  the  sexual  elements  at  the  same 
time.  The  changes  in  the  germs  would  everywhere  be  collateral, 
although  the  moments  when  any  of  the  changed  germs  hap- 
pened to  receive  their  development  might  be  different',, 


This  allusion  to  Mr.  Galton's  TJicory  of  Heredity 
leads  me  to  consider  what  Professor  Weisrnann  has 
said  with  regard  to  it  in  this  latest  publication, 
where,  for  the  first  time,  he  has  dealt  with  it. 
In  my  opinion  he  has  done  but  scant  justice  to  the 
views  of  his  predecessor,  and  therefore  I  will  occupy 
some  considerable  space  in  seeking  to  justify  this 
opinion. 

As  already  stated,  from  the  time  that  Mr.  Galton 
published  his  theory  I  have  felt  that  in  its  main  con- 
tention it  presents  a  probably  true  solution  of  the  main 
problem  of  heredity — viz.,  to  account  for  the  contrast 


'  Galiou,  loc.  cit.,  pp.  343-34-1. 


IVcisnuinnisnt  up  to  date  {1893). 


."> 


it  some 

3\vn  ac- 

gencra- 

csofthc 
chani^c 

Icmcnts. 
the  fol- 
primary 

oduction 

0  rc},^1rcl 
elopmcnt 
tly,  when 
;he   same 
'erywhcre 
n  whence 
w  variety 
cr  certain 
pectcd  to 
the  same 

1  collateral, 
rms  hap- 


Heredity 
lann  has 
3lication, 

with    it. 

e  to  the 
occupy 

itifv  thi>^ 

Galton 
lain  con- 
the  main 

contrast 


between  concijenital  and  acquired  cliaracters  in  respect 
of  transmissibility.     And    this   sokition,    as    likewise 
ah-eady  stated,  was  substaiiti  dly  identical  with  tliat 
which    Professor    VWismann    published    in    the    next 
decade.     Indeeil,  the   only  important   difference   be- 
tween these  two  theories  of    heredity  is,  tliat  while 
Wcismann's    excludes    on     deductive    grounds    the 
physioloL^ical  i)ossibility  of  the  inheritance  of  acquired 
characters,    Galton's    more   judiciously   leaves   to    be 
determined,  by  subsccjuent  encpiiry  of  the  inductive 
kind,   the  question   whether  acquired   ciiaracters  are 
ever  transmitted  in  faint  decrees,  or  whether  they  arc 
never  transmitted  at  all.    In  addition  to  this  important 
difference,   however,    there  are  certain    others   which 
seem  to  me  of  very  little  conseciuence.  inasmuch  as 
they  have  reference  to  speculations  on  the  ultimate 
mechanism  of  heredity,  or  the  intimate  morpholoi^y 
and  physiolof^y  of  the  carriers  of  heredity — specula- 
lations  which  it  wotdd  be  absurd  to  suppose  can  be 
other    than    purely    conjectural.     Therefore    in    my 
previous  criticism  I  did  not  allude  to  these  subordinate 
points   of  difference,   but   stated    merely,  in    general 
terms,  that  Galton's  view  of  the  ultimate  mechanism 
in  question  was  such  as  to  leave  room  for  the  possi- 
bility   of    the    occasional    transmission    of    acquired 
characters.     And  in  this  respect,  it  still  seems  to  me, 
his  theory  has  an  advantage  over  that  of  Weismann. 
No  doubt  the  latter  is  a  much  more  elaborate  and 
highly  finished   piece  of  work  ;    but  beauty  of  ideal 
construction  is  no  guarantee  of  scientific  truth — as  we 
shall  presently  find  exemplified  in  a  striking  manner 
with  regard  to  Weismann's  theory  of  evolution.     And 
if  his  theory  of  heredity,  in  its  final  shape,  is  a  mucli 

K  2 


« 


T 


It  •■ 


i 


•ill 


11' 


132    An  Exanmiation  of  Weisinannistn, 

more  precise,  detailed,  and  logically  coherent  structure 
than  any  which  has  ever  been  fraraed  in  this  depart- 
ment of  biological  thought,  there  is  all  the  more  reason 
to  scan  critically  the  fundamental  postulate  on  which 
it  rests.  Hence  I  cannot  help  feeling  that  it  will  be 
time  enough  to  consider  minor  differences  between 
the  two  theories  when  the  physiological  possibility  of 
the  occasional  transmission  of  ac([uired  characters,  as 
entertained  by  Galton's  theory,  shall  have  been  ruled 
out  as  demonstrably  opposed  to  fact. 

Seeing,  however,  that  Professor  Weismann  thinks 
otherwise,  and  ap[)ears  to  attach  as  much  importance 
to  differences  concerning  tleducti^-e  miuutiac  as  he 
does  to  those  concerning  fundamental  principles, 
I  will  here  contrast  the  two  theories  somewhat  more 
in  detail  than  heretofore,  and  with  special  refer- 
ence to  what  he  has  now  himself  said  touching  their 
relationship. 

It  will  be  remembered  that  the  primary  or  funda- 
mental difference  just  alluded  to  is,  that  while  the 
theory  of  germ-plasm  p')stulates  an  absolute  continuity, 
the  theory  of  stirp  postulates  but  a  partial  con- 
tinuity, of  the  substance  of  heredity.  Hence,  ac- 
cording to  We'smann's  view,  we  must  go  back  to 
the  unice'lular  organisms  for  the  origin  of  this  sub- 
stance in  the  multicellular  ;  and  we  must  regard  use- 
inheritance  as  physiologically  impossible.  On  the 
other  hand,  according  to  Galton's  view,  there  is  no 
necessity  for  us  to  do  'Mther  of  these  things.  The 
origin  of  stirp  is  to  be  found  in  the  somatic  tissues  of 
the  multicellular  organisms  themselves.  Nevertheless, 
this  theory  differs  greatly  from  i)angenesis,  in  that  the 
former  supposes  the  origin  of  hereditary  substance  to 


IVezsmannism  up  to  date  (189:).       133 


be  mainly  given  in  the  phylogcny  of  any  group  ol 
multicellular  organisms,  while  the  latter  sui^poscs  it  to 
be  given  mainly  in  each  ontogeny.  Galton's  theory  is, 
that  in  each  ontogeny  only  a  small  part  of  the  stirp 
derived  from  parents  is  consumed  in  making  the 
new  organism — the  larger  part  being  handed  over  in 
trust  for  passing  on  to  the  next  generation,  in  the 
same  way  as  Weismann  supposes  to  be  the  case  with 
germ-plasm.  Darwin's  theory,  on  the  other  hand, 
does  not  entertain  any  such  notion  of  "continuity" 
in  the  substance  of  heredity  from  gnrm-cell  to  germ- 
cell  of  parent  and  offspring ;  it  supposes  that  in 
each  successive  generation  the  gerni-cells  are  ivliolly 
supplied  with  their  germinal  material  from  somatic- 
cells  of  each  indi^•idual  organism.  Or,  adopting  our 
previous  terminology,  the  three  theories  may  be 
ranked  thus. 

The  particulate  elements  of  heredity  all  proceed 
centripetally  from  somatic-cells  to  germ-cells  (gem- 
mules)  :  the  inheritance  of  acquired  characters  is 
therefore  habitual. 

These  particulate  elements  proceed  for  the  most 
part,  though  not  exclusively,  from  germ-cells  to 
somatic-C(;l!3  (stirp) :  the  inheritance  of  acquired 
characters  is  therefore  but  occasional. 

The  elements   in  question   proceed  exclusively   in 
the  centrifugal  direction  last  mentioned  (germ-plasm; 
the    inheritance   of  acquired    characters    is   thercf  !o 
impossible  '. 


0 


'  I'rofessnr  Wcismnnn  still  jn:;irit;iins  tlint  thee  is  a  further  irnportint 
flistiiictioii  httwccii  tiic  thcniius  oJ  imii^ciicsis  mid  Ljeriii-plasni,  in  thai 
the  OIK'  is  ijrf.-formative  whilL-  the  oilier  is  e|>it;Liutic.  Jiiit  I  aiii  still 
iinnble  to  jurceive  that  such  is  the  c.ise.  He  ari^ucs,  indeed,  tiiat  his 
new  doctii;-,"  of  determinants  emphasizes  this  distinction  :    the  ar{^ament, 


134    ^^  Exaniination  of  Weisuiannism. 


\\m 


1      ! 


. 


1 


Such  bcinj:^  the  fundamental  points  of  difference 
between  these  three  theories  of  heredity,  we  have  now 
to  consider  more  particularly  those  which  obtain 
between  Galtons  and  Weismann's. 

The  jTcncral  doctrine  of  f^em mules  (i.  e.  somatic- 
cell-[^ernis)  is  accepted  by  Galton  :  but  instead  of 
supposing,  as  Darwin  supposed,  that  these  minute 
bodies  freely  circulate  through  all  the  body  tissues, 
so  that  some  of  them  arc  absorbed  from  all  the 
somatic-cells  by  the  q^erm-cells,  and  there  constitute 
the  entire  mass  of  hereditary  material  out  of  which 
the  offspring  will  afterwards  be  formed,  Galton  sup- 
poses that  gemmules  circulate  with  comparative  diffi- 
culty, and  that  only  comparatively  few  of  them  gain 
access  to  the  germ-cells  in  each  generation.  Hence, 
characters  acquired  in  the  individual  lifetime  are 
much  less  heritable  than  those  which  are  called  con- 
genital. For  congenital  characters  arc  due  to  the 
"continuity"  of  stirp  through  numberless  genera- 
tions in  the  phylogeny  of  the  organism  ;  hence  such 
characters  are  represented  by  a  vastly  greater  number 
of  equivalent  hereditary  elements.  Weismann,  on  the 
other  hand,  rejects  the  doctrine  of  gemmules  ///  toto. 

Again,   according    to    Galton 's    view,    "  individual 

however,  appenrs  to  me  radically  un'oiind.  For  instance,  he  says,  "  The 
hereditary  conliiuiati)!!  in  each  pan  is  pic-ckterniincd  in  each  jiail 
from  the  i;erm  onwards.  The  rii^lit  and  left  cars  could  not  possibly 
reseml)lc  each  other,  if  the  relative  strcni^th  of  the  hereditary  tendencies 
on  both  sides  were  not  ]ire-dcterniiiicd  for  all  jiarts  of  the  child  by  the 
nature  of  the  patiriial  and  material  idanls."  Very  well.  ]5uf.  if  so,  the 
theory  of  dcierniinants  is  jii.-t  as  much  jire-formative  as  is  that  of 
gemmules.  Or,  convi  isely,  the  latter  i«  quite  as  epi,<,"netic  as  the  former. 
Koth  are  alike  dctenniiiatirc.  while  neither  supposes  tliat  the  determina- 
tion is  due  to  a  ]iie-fornu'd  miuiaturo  of  tlir  Intuie  child  in  the  feriili/ed 
epp  of  its  mother;  but  to  a  particulate  representation  in  the  latter  of 
every  heritable  part  of  the  former. 


Wcisvianvisin  up  to  date  (1893).       135 

[congenital]  variation  depends  upon  two  factors ; 
the  one  is  the  variability  of  the  i^erm  '  and  of  its 
progeny  :  the  other  is  that  of  all  kinds  of  external 
circumstances,  in  determining  which  out  of  many 
competing  germs,  of  nearly  equal  suitability,  shall  be 
the  one  that  becomes  developed.  The  variability 
of  germs  under  changed  conditions,  and  that  of  their 
progeny,  may  be  small,  but  it  is  indubitable  ;  absolute 
uniformity  being  scarcely  conceivable  in  the  condition 
and  growth,  and,  therefore,  in  the  reproduction  of  any 
organism.  The  law  of  heredity  goes  no  further  than 
to  say,  that  like  tends  to  produce  like  ;  the  tendency 
may  be  very  strong,  but  jt  cannot  be  absolute-." 

Here,  of  course,  there  is  a  wide  difference  between 
stirp  and  germ-plasm.  For  while  Galton  does  not 
entertain  amphimixis  among  the  "  factors"  of  con- 
genital variation,  Weismann,  as  we  are  now  well 
aware,  has  hitherto  regarded  it  as  the  sole  cause 
of  such  variation.  Nevertheless,  as  we  shall  presently 
find,  Weismann  has  now  greatly  modified  his  views 
upon  this  point,  and  does  entertain,  in  The  Germ  lasvi. 
both  the  "  factors  "  mentioned  by  Galton.  Hence,  the 
difference  between  the  two  theories  in  question  with 
regard  to  this  matter  is  not  nearly  so  wide  as  it  was 
prior  to  the  publication  of  Weismann's  last  work. 

The  next  most  imi)ortant  point  of  difference 
between  the  theories  of  stirp  and  germ-plasm  has 
reference  to  the  mechanism  of  ontogeny.  Acc-^rding 
to  Galton,  this  is  simply  a  struggle  between  all  the 

•  lU'  "^erm"  Cinlton  means  a  carrier  of  hciedity,  which  is  capable 
of  sclf-muiU|ilicatiiiii.  In  thi.>c  fn.Mdamcntal  lespects.  ihcicforc,  it  is 
equivalent  to  a  "  j^riinmilo  "  on  the  one  hand  and  a  "determinant"  on 
the  other.     The  tiir;  c  II mis  are  so  far  synonymous. 

■^  Loc.  iit.,  p.  33S, 


WWflW-Uiill  if^iPF"Vl,PT/«^r^».  lufPJUUijii^'^PUu<ii>^'lii^ii«iniiMi^ivii»l 


S     fl! 


a    i| 


l!!|il 


136    An  Examination  of  IVeismanntsm. 

carriers  of  heredity  composing  the  stirp  of  a  fertilized 
ovum.  It  is  not,  however,  a  struggle  for  existence, 
but  what  may  be  called  a  struggle  for  development. 
In  the  fertilized  ovum  all  the  carriers  of  heredity  are, 
to  begin  with,  in  a  "  latent  "  condition  ;  but  of  this 
enormous  multitude  of  '•  germs  "  or  "  gemmules,"  only 
a  very  small  proportional  number  are  destined  to 
become  "  patent  " — i.  e.,  developed  into  the  tissue-cells 
composing  the  new  organism.  The  vast  majority 
of  the  gemmules,  or  those  which  fail  to  be  thus  de- 
veloped, go  to  constitute  the  stirp  of  the  new  organism 
when  this  has  been  formed  by  the  development  of  the 
comparatively  few  successful  gemmules.  Thus  much 
understood,  the  following  quotation  will  be  fully 
intelligible. 

My  argument  is  this  :  Of  the  two  groups  of  germs,  the 
one  consisting  of  those  that  succeed  in  becoming  developed 
and  in  forming  the  bodily  structure,  and  the  other  consisting  of 
those  that  remain  continually  latent,  the  latent  vastly  prepon- 
derates in  number.  We  should  expect  the  latent  germs  to 
exercise  a  corresponding  predominance  in  matters  of  heredity, 
unless  it  can  be  shown  that,  on  the  whole,  the  germ  tl  -^.t  is 
developed  into  a  cell  becomes  thereby  more  fertile  than  if  it  had 
remained  latent.  But  the  evidence  points  the  other  way.  It 
appears  both  that  the  period  of  feitility  is  shorter,  and  the 
fecundity  even  during  that  period  is  less  in  the  germ  that 
becomes  developed  into  a  cell,  th.m  they  are  in  the  gerai  that 
remains  latent.  Much  less  then  would  the  entire  bodily 
structure,  which  consists  of  a  relatively  small  number  of  these 
comparatively  sterile  units,  successfully  compete  in  matters  of 
heredity  with  the  'otal  eftect  of  the  much  more  numerous  and 
more  prolitic  units  which  are  in  a  latent  form'. 

Thus,  Galtons  theory  of  the  mechanism  of  onto- 

'   /.oc.  (it.,  p.  .'',,■',9. 


Ul 


•1    '■ 


'^.t    IS 


Weis7ttannis7n  up  to  date  (1893),       137 

geny  is  a  theory  of  struggle  ;  and  this  constitutes 
a  point  of  difference  on  which  Weismann  lays  much 
stress  in  his  latest  work.  For,  as  wc  know,  Weismann 
regards  the  mechanism  of  ontogeny  as  charac'.erized 
by  a  peaceful  succession  of  "  stages,"  which  are  "  pre- 
determined from  the  germ  onwards  ";  and  in  his  latest 
work  this  idea  of  orderly  sequence  has  been  further 
elaborated  in  his  doctrine  of  "determinants."  In 
short,  to  adopt  their  own  metaphors,  while  Galton 
tells  us  that  the  mechanism  of  ontogeny  is  like  that 
of  a  political  election,  where  rival  candidates  compete 
to  "  represent  "  the  nation  (stirp)  in  Parliament  (indi- 
vidual organism) ;  Weismann  likens  it  to  the  mechan- 
ism of  a  well-drilled  army,  where  ultimate  carriers 
of  heredity  (privates)  are  banded  together  in  com- 
panies, regiments,  battalions,  &c.,  under  the  command 
of  corresponding  officers  (determinants). 

Lastly,  there  is  yet  one  further  point  of  difference 
between  stirp  and  germ-plasm,  which  is  thus  stated 
by  We'smann  : — 

Galton's  idea  is  only  conceivable  on  the  presupposition  of  the 
occurrence  of  sexual  reproduction,  while  the  theory  of  the 
continuity  of  the  germ-plasm  is  entirely  independent  of  any 
assumption  as  to  whether  each  primary  constituent  is  present  in 
the  germ  singly  or  in  numbers.  According  to  my  idea,  the 
active  and  the  rcservj  , '.Tin -plasm  contain  precisely  similar 
primary  constituents,  gemmules,  or  dcttrminants ;  and  on  this 
the  resemblance  of  a  child  to  its  parent  depends.  The  theory 
of  the  continuity  of  the  germ-plasm,  as  I  undorstand  it,  is  not 
based  on  the  fact  that  each  "gemmule"  necessary  for  the  con- 
struction of  tile  soma  is  [)resent  many  times  only,  so  that  a  resiikie 
remains  from  which  the  germ-cells  of  the  next  generation  maybe 
formed  :  it  is  founded  on  the  view  of  the  existence  of  a  special 
adaptation,  which  is  inevitable  in  the  case  of  multicellular  organ- 
isms, and   which  consists  in  the   germ-plasm  of  the  fertilized 


m 

III 


^I 


iPli"  il»^  H)  VVJ 


if<m'f  '  t"i  I  ■  iiivmifirwf^rww^W 


1  ■  il 


:i!;i 


138    An  Exammation  of  Wcismannism. 

cgg-ccll  becoming  doubled  priniarily,one  of  the  resulting  portions 
being  reserved  for  the  lormation  of  gcnn-cells '. 

These  being  the  main  points  of  difference  between 
the  theories  of  stirp  and  of  germ-plasm  to  which 
Professor  Weismann  has  alluded,  I  will  now  proceed  to 
consider  them  separately,  in  reverse  order  to  that  in 
which  the\'  have  been  here  stated. 

The  point  of  difference  last  mentioned  need  not 
detain  us  long,  because  it  seems  to  me  one  of  very 
little  importance.  '•  Whether  each  primary  constituent 
is  present  in  the  germ  singly  or  in  numbers"  cannot 
greatly  signify,  so  long  as  both  theories  agree  that, 
sooner  or  latter,  they  must  be  present  plurally. 
Galton  supposes  them  to  be  thus  present  from  the 
first  (i.  e.  in  the  unfertilized  ovum),  while  Weismann 
supposes  them  to  be  so  only  as  a  result  of  their  self- 
multiplication  at  a  somewhat  later  stage  (i.  e.  in 
the  segmenting  ovum,  and  onwards  throughout  the 
procreativc  life  of  the  individual).  Doubtless  Weis- 
mann does  not  suppose  that  they  ever  become  so 
numerous  as  Galton  imagines  ;  but  the  whole  question 
is  so  highly  speculative  that  I  do  not  see  how  any 
useful  purpose  can  be  served  by  debating  it.  Nor  do 
I  see  why  Weismann  should  conclude  that  "  Galton's 
idea  is  only  conceivable  on  the  presupposition  of  the 
occurrence  of  sexual  reproduction."  It  is  true  that 
Galton  has  discussed  exclusively  the  case  of  sexual 
reproduction  ;  but  I  cannot  perceive  that  any  of  his 
ideas  are  inapplicable  to  a-.sexual. 

Touching  the  question  whether  the  phenomena  of 
ontogeny  had  best  be  ascribed  to  a  competition 
among   a  vast  number  of  "  germs,"  or  to  a  strictly 

'   The  (Jcnn-plasm,  pp.  199,  220. 


eismann 


Weis)naniiis))i  up  to  date  (1893).       ^39 

• 

ordered  evolution  of  a  comparatively  small  number 
of  "determinants,"  a  considerable  array  of  arguments 
might  be  adduced  in  support  of  either  view.  Thus, 
Galton  might  well  maintain  that  his  interpictation 
of  the  observable  facts  is  most  in  accordance  with  the 
general  analogies  sup[)lied  by  organic  nature  as  a 
whole.  The  ancient  aphorism  of  Heraclitus, ''  Struggle 
is  the  father,  king,  and  lord  of  all  tilings,"  has  been  in 
large  measure  justified  by  Darwin  and  his  followers, 
at  any  rate  within  the  range  of  biology.  Not  only 
have  we  the  "  strucfcfle  for  existence"  where  "the 
origin  of  si^ecics  "  is  concerned  ;  but  Roux  has  well 
argued,  in  his  remarkable  work  on  Dcr  KcDiipf  dcr 
Tlicilcivi  Orj^a?iis?Nus, that  the  principle  of  "struggle" 
is  concerned  to  an  equally  im[)oitant  extent  as 
between  all  the  constituent  parts  of  the  same  indi- 
vidual. J^ut  if  this  is  so — if  every  tissue-cell  of  the 
organism  owes  its  maintenance  to  success  in  a  general 
contest  for  nutriment,  &c., — do  we  not  find  at  least 
a  probability  that  it  owes  its  origin  as  a  visible 
cell  to  a  similar  success  in  a  similarly  general  contest 
among  the  invisible  elements  Irom  which  tissue-cells 
arc  de/elo[:)ed?  Nay,  does  it  not  seem  well  nigh 
incredible  that  when  this  selection-principle  is  seen  to 
be  the  governing  cause  of  evoluticMi  everywhere  else, 
it  should  cease  to  play  any  part  at  all  just  at  the 
place  where  we  are  unable  to  see  what  is  going  on  ? 
As  we  are  agreed  that  this  ''  father  of  all  thinfrs  " 
is  of  prime  importance  in  phylogeny — to  say  nothing 
of  physiology,  psychology,  and  sociology.  -  must  we 
not  deem  it  absurd  to  suppose  th.it  it  ' .  supplanted 
in  ontogeny  by  the  opposite  principle  of  absolute 
peace  ? 


R 


I 


■^  I  ip^  wwi^  il^lnilHIIIil 


,1   i 


140    An  Examination  of  Weis^nannism. 

On  the  other  hand,  Weismann  adduces  many 
forcible  considerations  per  contra  ;  so  that,  in  the 
result,  I  deem  it  best  to  dispose  of  the  question  with 
two  general  remarks.  The  first  is,  that  the  rival  views 
are  not  necessarily  incompatible.  Each  may  present 
one  aspect  of  the  truth.  Weismann's  doctrine  of 
determinants  may  be— and,  to  the  best  of  my  judge- 
ment, must  be — sound  ;  but  this  does  not  hinder  that 
Gallon's  doctrine  of  struggling  "  germs "  may  be  so 
likewise.  For,  as  we  have  already  seen,  these  germs 
present  the  same  compound  character  which  belong 
to  determinants  ;  in  fact  I  do  not  suppose  that  Galton 
would  object  to  identifying  them  with  determinants. 
On  the  other  hand,  I  do  not  see  why  Weismann 
should  object  to  supposing  that  similar  determinants 
compete  among  themselves  for  ontogenetic  develop- 
ment. Indeed,  he  has  already  argued,  in  his 
suggestive  theory  of  "germ-tracts,"  that  it  is  usually 
only  one  among  a  number  of  similar  determinants 
which  does  succeed  in  achi(  ving  such  development — 
or,  as  he  expresses  it,  whi  '^  "  becomes  active."'  But 
what  is  it  that  causes  this  activity?  Surely  it  must  be 
some  superiority  on  the  part  of  the  active  determinant 
over  its  passive  companions.  And,  if  so,  it  is  the 
selection-principle  that  is  here  at  work.  In  fact,  he 
has  himself  laid  no  small  stress  on  what  he  calls  "the 
struggle  of  the  determinants  of  the  two  parents  in 
ontogeny,"  and  has  even  supplied  a  long  section  op 
''  the  Struggle  of  the  Ids  in  Ontogeny."  Therefore 
I  do  not  see  why  he  should  so  emphatically  dissent 
from  Galton's  view  upon  this  matter  as  he  does 
in  his  work  on  The  Gcnu-phisin'^. 


Weismaiinisni  up  to  date  (1893).       141 

My  second  remark  is  a  brief  one — viz.,  that  the 
\vln)le  (juestioii  is  of  so  very  speculative  a  character, 
that  I  cannot  sec  the  smallest  use  in  debatini;  it. 

The  only  remainintj  point  of  difference  between 
strip  and  germ-plasm  is  the  one  referring  to  stability. 
Needless  to  sa>',  Galton  is  at  one  with  Weismann  in 
recognizing  a  high  degree  of  stability  on  the  part  of 
the  substance  of  heredity  ;  but  the  agreement  extends 
only  so  far  as  is  necessitated  by  the  facts  of  atavism, 
&c.  Indeed,  he  does  not  even  mention— although  he 
l)erhaps  implies  what  Weismann  has  called  ami)hi- 
mixis  as  among  the  factors  of  individual  congenital 
variation.  W'eismaiui,  on  the  other  hand,  has  hitherto 
regarded  am[)himixis  as  the  sole  cause  of  all  such 
variations.  But.  as  we  shall  presently  find,  in  his 
recent  work  on  y/ic  Gcnn-plasin  he  has  now  greatly 
modified  his  views  upon  this  subject,  and,  in  fully 
recognizing  the  ''factors''  of  variability  to  which 
Galton  alludes,  has  corresi)ondingIy  lessened  the 
ilifference  between  germ-plasm  and  stirp.  But  this  is 
a  point  which  can  be  better  dealt  with  when  we  come 
to  consider  the  important  modifications  which  in  this 
respect  the  theory  of  germ-plasm  has  undergone. 


The  only  other  matter  which  has  to  be  mentioned 
in  connexion  with  Weismann's  theory  of  heredity  is, 
that  in  The  Gcj-m-plasmhn  has  for  the  first  time  given 
us  his  views  upon  the  influence  of  a  previous  sire  on 
the  progeny  of  a  subsequent  one  by  the  same  dam. 
The  phenomena  in  question,  which  I  have  already 
detailed  in  pp.  77-9,  110.  he  designates  by  the  term 
"telegony."  The  analogous  phenomena  in  plants  he 
calls,  followuig  Focke,  "  xenia." 


Ill 

it 


^w-fW<nrm<W'^ 


i      t 


142    An  Ex'.iuiitiation  of  IVcisniaiinism. 

With  regard  to  tclcgony,  he  adopts,  almost  pre- 
cisely, the  position  which  I  surmised  that  he  would. 
That  is  to  say,  he  first  disputes  the  alleged  facts,  and 
then  argues  that,  even  if  they  be  facts,  they  admit  of 
being  explained  on  the  theory  of  germ-plasm  by 
supposing  that  some  of  the  germ-plasm  from  the 
first  sire  penetrates  the  unripe  ova  which  are  after- 
wards fertilized  by  the  second  '.  The  only  difference 
between  his  views  and  my  own  upon  this  matter  is, 
therefore,  as  follows. 

Supposing  that  the  phenomena  alleged  ever  occur 
in  fact,  I  have  said  that  the  only  way  of  explaining 
them  would  seem  to  be,  '•  that  the  life  of  '  germ-plasm ' 
is  not  conterminous  with  that  of  the  spermatozoa  which 
convey  it,  and  hence  that,  if  the  carriers  of  heredity, 
after  the  disintegration  of  their  contninnig  sperma- 
tozoa, should  ever  penetrate  an  unripe  ovum,  the 
germ-plasm  thus  introduced  might  remain  dormant 
in  the  ovum  until  the  latter  becomes  mature,  and  is 
then  fertilized  by  another  sire.  In  this  way  it  is  con- 
ceivable that  the  hitherto  dormant  germ-plasm  of  the 
previous  sire  might  exercise  some  influence  on  the 
ontogeny  of  the  embryo  -." 

Now,  this  is  substantially  the  position  which  Weis- 
mann  takes  up  ;  only  instead  of  supposing  that  it  is 
the  "  carriers  of  heredity  "  of  the  first  sire  which  gain 
access  to  the  unripe  ovum  "  after  the  disintegration 
of  their  containing  spermatozoa,"  he  supposes  that  it 
is  one  of  the  spermatozoa  which  does  so  before  its 
disintegration  has  commenced.  Of  course  there  is 
here  no  difference  in  principle,  but  only  a  question 
touching  the  mode  in  which  the  access  is  presumably 

'   The  Germ-plasm,  pp.  383-386.  2  Quoted  troin  above,  p.  78. 


Wcisfiiaiinisifi  up  to  date  (1S9;).       14;^ 

effected.  But,  as  rec^ards  this  question,  I  retain  my 
original  opinion.  For,  while  I  can  see  no  theoretical 
difficulty  in  supposing  that  ''the  carriers  of  heredity,'' 
when  set  free  by  the  disintegration  of  their  containing 
spermatozoa,  may  reacli  the  unripe  ova  while  still 
embedded  in  the  depths  of  the  ovary,  I  do  see  a 
difficulty,  amounting  almost  to  a  physiological  im- 
possibility, in  supposing  that  a  whole  spermatozoon 
can  perform  such  a  feat.  From  all  that  we  know 
about  the  powers  and  functions  of  spermatozoa  in  the 
vertcbrata,  it  appears  simply  absurd  to  imagine  that 
these  bodies  are  able  to  penetrate  the  dense  coating  of 
an  ovary,  and  then  delve  their  way  through  the  stroma. 
There  is,  indeed,  a  remarkable  investigation  which 
was  published  a  year  or  two  ago  by  Mr.  Whitman  ^ 
which  appears  to  prove  that  in  certain  leeches  the  male 
injects  his  seminal  fluid  into  any  part  of  the  body  of 
the  female,  and  that  the  spermatozoa  then  reach  the 
ova  by  wandering  about  her  general  tissues  until  some 
of  them  happen  to  hit  upon  her  ovary.  But  in  this 
case  the  spermatozoa  are  specially  adai)ted  to  perform 
such  acts  of  penetration — being  spear-like  bodies 
provided  with  a  sharp  point.  Hence,  if  Weismann 
should  quote  this  instance,  it  would  not  tend  to 
support  his  view,  seeing  that  the  spermatozoa  of 
mammals  do  not  exhibit  any  such  specializations  of 
structure  ;  and  therefore,  before  any  one  of  them  can 
effect  fertilization,  must  wait  for  the  ovum  to  mature, 
reach  the  surface  of  the  ovary,  and  rupture  its  follicle. 
But,  as  already  observed,  it  docs  not  signify,  so 
far  as  we  are  here  concerned  with  the  matter,  in  what 
precise    manner   the    telegonous    influence    may    be 

'  Alorph.  Journal,  vol.  ii. 


144    "'^^^  Exaniinatioti  of  Wcis))ianni$m. 

sui)po.scd  to  be  exercised — provided  tliat  it  may  be 
so  directly,  and  not  necessarily  tiirouj^h  first  having 
to  influence  the  whole  material  organism.  Therefore 
I  quite  a;^n-ce  with  VVeisniann  that  the  facts — sup- 
posinfj  them  to  be  facts — are  quite  as  explicable  by 
the  theory  of  |jjerm-i)lasm  as  by  that  of  panj;enesis  ^ 
A<^ain,  with  resi)ect  to  xenia.  VVeismann  writes  : — 

As  such  I'liiincnt  botanists  ;is  Kockc,  unci  inure  recently 
I)e  Vries,  have  expressed  nuich  doubt  with  rei;ard  to  these  obse*-- 
vations— or  rather  interpretations  we  nuist  wait  until  these 
cases  have  been  critically  re-investi,^'ated  before  atteinptin^^  to 
account  for  them  theoretically.  The  chief  difriculty  we  should 
meet  with  in  any  such  explmation  would  be  due  to  the  fact  that 
weare  here  concerni'd  with  ilie  innuence  of  the^'t77;/-/Arv///  of  the 
sperm-cell  on  a  tissue  of  another  plant  which  only  constitutes 
a  pixrt  of  this  plant.  It  wt)uld  thus  be  necessary  to  assume  that 
all  the  determinants  of  this  j^erm-plasm  are  not  activCj  and  that 
only  those  take  erferl  which  determine  the  nature  of  the  fruit. 

Now,  it  docs  not  a[)pcar  that  I)c  Vries  has  looked 
into  the  matter  on  his  own  account,  as  he  merely 
refers  to  what  Focke  has  said.  And  this  amounts 
merely  to  showini;  the  dubious  character  of  some 
half-dozen  cases  which  Focke  o;ives  as  those  which 
alone  have  fallen  within  his  coLjnizance.  Why  he 
does  not  mention  an)'  of  the  numerous  cases  which 
are  quoted  by  Darwin,  I  do  not  understand.  Nor 
can  I  understand  why  he  does  not  consider  what  seem 
to  be  the  particularly  conclusive  facts  given  on 
p.  80, — i.e.,  where  xenia  api)cars  to  constitute  "a 
needful  preliminary  to  fertilization."  But  the  whole 
matter  is  one  for  botanists  to  deal  with,  and  if  any 
doubt  attaches  to  it,  at  least  the  grounds  of  such 
doubt    should    be    fully   stated.     Still    more,   in  my 

'  See  Appendix  II. 


IVcisiiiautiisin  up  to  date  (iiSq;,).        145 

opinion,  should  the  matter  be  freed  from  any  such 
doubt.  The  ([uestion — if  there  be  a  question — is  one 
of  ^rcat  interest  from  a  merely  physiological  i)oint 
of  view,  while  in  relation  to  the  fundamental 
problems  of  heredity  its  importance  is  immense. 
Surely,  then,  any  competent  botatu'st  who  disi)utcs 
'^he  facts  ought  to  test  them  by  way  of  experiment. 

Ikit,  be  this  as  it  may,  I  must  call  prominent 
attention  to  the  following  very  remarkaljle  words 
wherewith  Weismann  concludes  the  passage  above 
quoted.  For  he  there  says,  that  even  supposing  there 
were  no  doubt  as  to  the  facts  or  their  interpretation, 
''the  chief  difficulty"  which  they  would  oppose  to 
the  theory  of  germ-plasm  would  be,  "  that  we  are 
here  concerned  with  the  influence  of  the  s^cnn-p/asm 
of  the  sperm-cell  on  a  tissue  of  another  plant  which 
only  constitutes  a  part  of  this  plant."  In  other  words, 
Weismann  now  freely  entertains  the  possibility  of  a 
direct  action  of  germ  plasm  on  the  somatic  tissues, 
even  though  these  belong  to  another  individual ! 
Thus  he  now  concedes  the  only  point  for  the 
establishment  of  which  I  adduced  the  phenomena 
of  xenia,  in  Chapter  III  :  the  whole  of  one  side 
of  that  "  reciprocal  action  between  the  sphere  of 
germinal-substance  and  the  si)hcre  of  body-sub- 
stance," which  I  contended  for  on  pp.  76-S;'5,  is  now 
conceded  ;  and  although  it  is  the  less  important 
side,  its  surrender  goes  far  to  weaken  the  doctrine 
of  a  per[)etual  isolation  of  germinal-substance  to 
a  "sphere"  of  its  own.  If  we  suppose  that  the 
germinal  substance  of  one  organism  may  thus 
directly  act  upon  the  somatic  tissues  of  another, 
and   that   changed   conditions    of    life    are    able   to 

L 


146    An  Bxainination  of  IVeisinaunism. 

produce  simultaneously  an  acquired  character  in 
the  soma  and  a  precisely  identical  character  as 
congenital  in  the  germ  (pp.  129-30),  we  are  plainly 
inviting  ourselves  to  abandon  the  complex  explana- 
tion of  living  material  in  '•  twd  kinds,"  where  one  is 
capable  in  .ill  sorts  of  way?  of  communicating  with 
the  other,  while  the  possibility  of  any  reciprocal  action 
is  excluded.  For  the  simpler  hypothesis  of  living 
material  as  all  of  one  kind  encounters  no  such 
antinomies.  So  long  as  one  kind  of  this  material 
was  supposed  to  be  as  distinct  from  the  other  as  a 
parasite  is  distinct  from  its  host,  there  was  not  so 
much  to  choose  between  the  theory  of  germ-plasm 
and  that  of  gem  mules  in  this  respect  of  simplicity. 
But  the  more  that  the  former  theory  has  had  to  be 
adjusted  to  facts,  the  greater  has  its  complexity 
become,  until  now  its  own  author  is  obli 'jjed  to  make 
SO  many  additional  assumptions  for  the  purpose 
of  maintaining  it,  that  we  begin  to  wonder  how  long 
it  can  continue  to  support  the  weight  of  its  accuma- 
lating  difficulties. 

So  ruich  for  the  m'lln  modifications  which  have 
this  year  been  made  in  Weismann's  postulate  of  the 
periietual  contitiuity  of  germ-[)lasm.  We  must  next 
consider  the  changes  which  he  has  effected  in  his 
companion  postulate  of  the  absolute  stability  of 
germ-plasm. 


•w»™^^rTV»W*'"'ivi!  11  |i,l!*W  ■ 


fP 


Weismanmsm  up  to  date  (1893).       ^47 


Weisvimuis  Theory  of  livoliition  (1H93). 


Of  far  more  importance  than  any  of  the  alterations 
whicli  Professor  Weismann  has  rccenti)'  made  in  his 
theory  of  heredity,  are  those  whereby  he  has  modi- 
fied his  sequent  theory  of  evolution.  For  while, 
as  we  have  just  seen,  his  work  on  TJic  Gaiii-plasui 
leaves  the  former  theory  substantially  unaltered -- 
althoui^h  largely  added  to  '\\\  matters  of  detail. — it 
so  profoundly  modifies  the  latter  tluit  careful  readers 
will  find  no  small  difficulty  in  ascertaining  how  much 
of  it  has  been  allowed  to  remain.  I  will  consider 
only  the  main  modifications,  and  these  I  will  take 
separately. 


1 

i 


, 


I   ;  >{ 


It  will  be  rememberetl  that  one  distinctive  feature; 
in  Weismanns  theory  of  evolution  has  hitherto  been, 
that  the  unicellular  organisms  differ  from  the  multi- 
cellular in  the  following  important  i)articu]ars. 

1.  lliere  being  no  division  in  unicellular  organisms 
between  germ-cells  and  somatic-cells,  there  is  n<^ 
possibility  in  them  of  the  occurrence  of  amphimixis. 

2.  Consequently,  there  is  no  possibility  in  them  of 
congenital  variations,  in  the  sense  that  these  occur 
in  multicellular  organisms. 

3.  Hence  the  only  causes  of  individual  variation 
and  of  the  origin  of  species  in  the  unicellular  organ- 
isms are  the  Lamarckian  factors,  just  as  in  the  multi- 
cellular the  only  cause  ol  these  things  is  natural 
selection. 

4.  Hence,  also,  the  unicellular  orgp.nisms  arc  poten- 


Via 


^ 


148    All  Exaviination  of  Wcisviannism. 

tially  immortal,  while  the  multicellular  have  acquired 
mortality  for  certain  adaptive  reasons. 

But  now,  with  the  exception  of  No.  4,  all  these 
positions  have  been  abandoned.  For,  chiefly  on 
account  of  the  beautiful  researches  of  Maupas,  Weis- 
mann  has  come  to  perceive  that  no  real  distinction 
can  be  drawn  between  an  act  of  sexual  union  in 
the  multicellular  organisms,  and  an  act  of  conjuga- 
tion in  the  unicellular.  Amphimixis,  therefore,  is 
now  held  by  him  to  occur  equally  in  both  these 
divisions  of  organic  nature,  with  the  consequence 
that  the  Protozoa  and  Protophyta  owe  their  indi- 
vidual variations,  and  therefore  the  origin  of  their 
innumerable  species,  as  exclusively  to  the  action 
of  natural  selection  as  is  the  case  with  the  Metazoa 
and  Metaphyta.  In  fact,  the  term  "amphimixis  "  has 
been  coined  in  express  relation  to  these  very  points. 

It  will  be  seen,  however,  that  this  important  change 
of  view  merely  postpones  the  question  as  to  the 
origin  of  amphimixis,  if  the  object  of  this  process  be 
that  which  Weismann  supposes — viz.,  the  providing  of 
material  in  the  w^ay  of  congenital  variations  on  which 
natural  selection  can  act.  Therefore  he  is  obliged 
to  assume  that  there  now  are,  or  once  have  been, 
organisms  of  a  less  organized  character  than  even  the 
lowest  of  the  unicellular  forms — organsims,  that  is 
to  say,  which  possess  no  nucleus,  but  are  wholly 
composed  of  undifferentiated  bioplasm.  These  most 
primitive  organisms  it  must  have  been  that  were  not 
subject  to  any  process  of  natural  selection,  but,  in  virtue 
of  an  exclusive  action  of  the  Lamarckian  factors  upon 
their  protoplasmic  substance,  gave  rise  to  individual 
variations  which  subsequently  gave  rise  to  a  unicellular 


Wcismannism  tip  to  date  (1893).       149 


:ss  be 

inij  of 

which 

)bH'j:cd 


progeny— when  the  process  of  natural  selection  was 
immediately  inaugurated,  and  thereafter  entirely 
superseded  the  Lamarckian  factors.  Or,  to  state  the 
matter  in  VVeismann's  own  words  : — 

IVIy  earlier  views  f)n  unicellular  organisms  as  the  source  of 
individual  dilTerenrcs,  in  the  sense  that  each  chani^e  called  forth 
in  them  by  external  intliiences,  or  by  use  and  disuse,  Vviis 
sup[)osecl  '  ■  be  hereditary,  must  therefore  be  dismissed  to  some 
sta;4e  less  distant  frt)m  the  orii^in  of  life.  I  now  l)elieve  that 
oUch  reactions  under  external  influences  can  only  obtain  in  the 
lowest  organisms  which  are  without  any  distinctii'n  between 
nucleus  and  cell-body.  All  variations  which  have  arisen  in 
them,  by  the  ojieration  of  any  causes  whatever,  must  be  in- 
herited, and  their  htreditaiy  individual  varial)ility  is  due  to  the 

direct  influence  of  the  external  world If  I  am  correct  in 

my  view  of  the  meaning  of  conjugation  as  a  method  of  amphi- 
mixis, wc  must  believe  that  all  unicellular  organisms  possess  it, 
and  that  it  wiJ  be  found  in  numerous  low  organisms,  in  which 
it  has  not  yet  been  observed  '. 

It  is  not  very  clear,  at  first  sight,  how  Professor 
Wcismann,  after  having  thus  abandoned  the  pro- 
positions 1 .  2,  and  3,  as  above  stated,  manages  to  retain 
his  former  view  as  given  in  No.  4.  Nevertheless  he 
does  so,  by  representing  that  a  unicellular  organism, 
even  though  it  present  such  a  considerable  degree  of 
organization  as  we  meet  with  in  the  hicfher  Protozoa, 
still  resembles  a  germ-cell  of  a  multicellular  organism, 
in  that  it  consists  of  all  the  essential  constituents  of 
a  germ-cell,  inchiding  germ-plasm  in  its  nucleus.  And 
inasmuch  as  a  germ-cell  is  potentially  immortal,  so  it 
must  be  with  a  unicelluUar  organism ;  in  the  one 
case,  as  in  the  other,  the  design  of  the  structure  is 
that  its  contained  germ-plasm  shall  ftise  with  the  germ- 
plasm  contained  in  the  nucleus  of  another  individual 
'  Essays  on  Heredity,  vol.  ii.  pp.  193-4. 


150    An  Exahiinatioii  of  Weismannism. 


J;!»i 


«'     ' 


cell,  when  the  life  of  both  will  be  preserved.  For 
my  own  part,  however,  I  cannot  see  that  in  either 
case  the  ccl^  hs  distinguished  from  its  contained  ^^r;«- 
plasni,  is  thus  shown  to  be  potentially  immortal.  On 
the  contrary,  it  appears  to  me  a  mere  accident  of 
the  case  that  in  a  unicellular  organism  the  immortal 
substanc  (germ-plasm)  is  contained  in  a  single  cell, 
which  is  at  the  same  time  2,  free  cell,  and,  as  such,  is 
denominated  an  ''organism."  We  might  just  as  well 
call  a  LTcrm-cell  an  "orcranism."  whether  a'^  an  ovum 
it  happens  to  be  embedded  in  a  mass  of  somatic-cells, 
or  as  a  locomotive  spermatozoon  it  happens  to  be 
free.  In  fact  Wcismann  himself  appears  to  recognize 
this.  P)Ut,  if  .so,  it  is  surely  a  distinction  without 
a  difference  to  say  that  unicellular  organisms  are 
immortal,  while  m\ilticcllular  are  mortal.  h'or  in 
neither  case  is  the  organism  immortal,  while  in  both 
cases  it  is  the  germ-plasm  (i.e.,  the  substance  of  heredity) 
that  is  .so.  Where  the  cell  containini?  the  ecrm-plasm 
happens  to  be  a  irce  cell,  it  is  called  an  "  organism  "  ; 
but  whether  it  be  a  germ-cell  or  a  protozoan,  it  alike 
ceases  to  be  a  cell  when  it  has  Qiven  oricfin  to  a 
multitude  of  other  cells,  whether  the.se  happen  to  be 
other  germ-cells  {plus  somatic-cells)  or  other  proto- 
zoan cells.  In  short,  qua  cell,  all  cells  arc  mortal  : 
it  is  only  the  .substance  of  heredity  which  some  ceils 
contain  that  can  be  said,  in  any  sense  of  the  term,  to 
be  immortal.  Vox  the  immortality  in  question  does 
not  belong  to  unicellular  organisms  as  such,  but  to  the 
germ-plasm  whicii  they  contain.  And  from  this  it 
follows  that,  as  the  immortality  of  germ-plasm  is 
one  and  the  .same  thing  as  the  continuity  of  germ- 
plasm,   by  alleging  an  immortality  as  belonging   to 


Weisma7iiiisin  up  to  date  (1893).       151 

the  unicellular  ori^anisms,  Wcismann  is  merely  re- 
stating his  fundamental  postulate.  Hence,  also,  he 
is^  but  dcnyin^^,  in  a  somewhat  round-about  way,  the 
occurrence  of  spontaneous  generation. 

I  conclude,  therefore,  that  his  sole  remaining 
distinction  between  the  unicellular  and  the  multi- 
cellular organisms  is  but  illusory,  or  unreal.  And, 
with  recrard  to  the  great  change  which  he  has  thus 
effected  in  his  system  b}'  xpressly  abolishing  all  the 
other  distinctions,  I  have  only  to  say  that  in  my 
opinion  he  has  thereby  greatly  iniprovctl  his  system. 
For  he  has  thus  relieved  it  of  all  the  formidable 
difficulties  which  he  had  needlessly  created  for  him- 
self, and  which  I  have  alrcadv  enumerated  in  the 
foregoing  pages  (88-M9).  In  his  ever-shifting  drama 
of  evolution  the  unicellular  organisms  have  left  the 
stage  en  masse,  and,  so  far  as  they  are  concerned, 
we  arc  all  as  wc  were  before  the  curtain  rose. 


But  of  even  more  importance  than  this  funda- 
mental change  of  view  with  regard  to  the  unicellular 
organisms,  is  a  further  and  no  less  fundamental 
change  with  regard  to  the  multicellular.  That  such 
is  the  case  will  immediately  become  apparent  by 
a  simple  statement  of  the  fact,  that  Weismann  has 
now  expressly  surrendered  his  postulate  of  the  abso- 
lute stability  of  germ-plasm  ! 

We  have  already  seen  that,  even  in  the  first  volume 
of  his  Essays,  there  were  some  passages  which  gave 
an  uncertain  sound  with  regard  to  this  matter.  But 
as  they  seemed  attributable  to  mere  carelessness  on 
the  })art  of  their  author,  after  quoting  a  sample 
of  them,  I  showed  it  was  necessary  to  ignore  such 


BJ 


5 


152    An  Examination  of  Weismannism. 

inconsistent  utterances — necessary,  that  is,  for  the 
purpose  of  examining  the  theory  of  germ-plasm  as 
even  so  much  as  a  logically  coherent  system  of  ideas  ^. 
For  \vc  have  seen  that  if  any  doubt  were  to  be 
entertained  touching  the  absolute  stability  of  germ- 
plr.sm  "since  the  first  origin  of  sexual  propagation," 
a,  corresponding  measure  of  doubt  would  be  cast  on 
Wcismann's  theory  of  congenital  variation  as  solely 
due  to  amphimixis,  with  the  result  that  his  whole 
theory  of  evolution  would  be  similarly  rendered 
dubious.  Since  then,  however,  he  has  gone  very 
much  further  in  this  direction.  First,  in  reply  to 
Professor  Vines  he  says  (1  ^90) : — 

i  am  at  present  inclined  to  believe  that  Professor  Vines  is 
correct  in  questioning  whether  sexual  reproduction  is  the  only 
factor  which  maintains  Metazoa  and  Metaphyta  in  a  state  of 
variability.  I  could  have  pointed  out  in  the  English  edition 
of  my  "Essays"  that  my  views  on  this  point  had  altered  since 
their  publication  ;  my  friend  Professor  da  Bary,  too  early  lost  to 
science,  had  already  called  my  attention  tD  those  parthenogenetic 
Fungi  which  I'rofessor  Vines  justly  citef,  agairst  my  views;  but 
I  desired,  on  grounds  already  mentioned,  to  undertake  no  altera- 
tion in  the  essays  ". 

Next,  in  his  essay  on  AinpJdmixis  (1892),  there  are 
several  passages  to  somewhat  the  same  eiTect ;  while, 
lastly,  in  his  Germ-plasm  (1^)93),  the  fun("imental 
postulate  in  question  is,  as  I  have  said,  expressly 
surrendered.  For  example,  we  have  in  the  following 
words  the  final  conclusions  of  his  recent  arguments. 
Speaking  of  amphimixis,  he  says  : — 

//  is  not  the  primary  cause  of  hereditary  variation.  P>y  its 
means  those  specilic  variations  which  already  exist  in  a  species 


'  See  above,  pp.  6,v^>7- 


Wit  lire,  vol.  xli.  p.  322. 


IVcismannisDi  up  to  date  (1893).       153 

may  continually  be  blended  in  a  fresh  manner,  but  it  is  incap- 
able of  giving  rise  to  new  variations,  even  though  it  often 
appears  to  do  so.  .  ,  .  'J'hc  otitsc  of  hereditary  xniriation  must  lie 
deeper  than  this.  It  must  be  due  to  the  direct  effects  of  external 
influences  on  the  biophores  and determinanis\ 

These  quotations  are  cnoiicjh  to  show  that  Wcis- 
mann  has  now  abandoned  his  original  theory  of 
congenital  variations  being  exclusively  due  to  amphi- 
mixis, and  adopts  in  its  stead  the  precisely  opposite 
view — viz.,  that  the  origin  of  all  such  variations  must 
be  ascribed  to  the  direct  influence  of  causes  acting  (mi 
germ-plasm  from  without.  Up  to  the  present  year 
the  very  essence  of  the  whole  Weismannian  theory 
of  evolution  has  been  that,  owing  to  the  stability 
of  germ-plasm  since  the  first  origin  of  sexual  pro- 
pagation, "the  origin  of  hereditary  individual  varia- 
tions cannot  indeed  be  found  in  the  higher  organisms, 
the  Metazoa  and  Metaphyta  ;  but  is  to  be  sought 
for  in  the  lowest — the  unicellular  organisms,"  because 
"  the  formation  of  new  species,  which  among  the 
lower  Protozoa  cotdd  be  achieved  without  amphigony, 
could  only  be  attained  by  means  of  this  process  in 
the  Metazoa  and  Metaphyta.  It  was  only  in  this 
way  that  hereditary  individual  differences  could  arise 
and  persist  V 

But  about  the  beginning  of  the  present  year  we 
have  this  fundamental  doctrine  directly  contradicted 
in  such  words  as  :  — 

The  origin  of  a  variation  is  equally  independent  of  selection 
and  amphimixis,  and  is  due  to  llie  constant  occurrence  of  slight 
inequalities  of  nutrition  in  the  germ-plasm  '. 

*   The  Germ-plnsm,  pp.  414-415.     IlnliLS  Wci^mmin's. 
-  Essays,  vol.  i.  p.  2S4.  The  (Jenii-/>liisin,  p.  431, 


I 


154    ^^  Examination  of  Weismannism. 


li 


m 


'    l':\ 


This  complete  reversal  of  his  previous  doctrine 
brings  Weismann  into  line  with  Darwin,  who  long 
ago  gave  very  good  reasons  for  the  following  con- 
clusion : — 

Those  authors  who,  like  Pallas,  attribute  all  variability  to  the 
crnssin>i  cither  of  distinct  races,  or  to  distinct  individuals  belong- 
ing to  the  same  race  but  somewhat  different  from  each  other, 
are  in  error;  as  are  those  authors  who  attribute  all  variabi'ty 
to  the  mere  act  of  sexual  union  \iii}iphiviixis\  *. 

And  again  : — 

These  several  considerations  alone  render  it  probable  that 
variability  of  every  kind  is  directly  or  indirectly  caused  by 
changed  conditions  of  life.  O;,  to  put  it  under  another  point 
of  view,  if  it  were  possible  to  expose  all  the  individuals  of  a 
species  during  many  generations  to  absolutely  uniform  con- 
ditions of  life,  there  would  be  no  variability'''. 

Hence,  Darwin  was  disposed  to  find  the  main, 
if  not  the  only,  causes  of  congenital  variations  in 
circumstances  depending  for  their  efficacy  on  the 
iustability  of  what  Weismann  calls  gcrm-plasm.  And 
the  noteworthy  fact  is,  that  Weismann  has  now 
adopted  this  view,  to  the  destruction  of  his  originally 
fundamental  postulate  touching  the  stability  of  germ- 
plasm  since  the  first  origin  of  sexual  propagation. 

By  such  a  right-about-face  manoeuvre.  Weismann 
has  placed  his  critics  in  a  somewhat  difficult  position. 
For,  in  the  first  place,  it  is  only  towards  the  close 
of  T/ie  Gcrni-plasin  that  the  manoeuvre  is  executed, 
and  then  only  in  a  few  sentences  such  as  1  have  just 
quoted— italici/.ed,  it  is  true,  but  otherwise  so  slightly 


I 


*   Vai  iation  &.c.,  vol.  i.  p.  .vjH. 


/I'll/.,  vol.  ii.  p.  242. 


Weisinannisju  tip  to  date  (1893).       155 

emphasized  that,  as  Professor  Hartof]^  has  observed, 
no  one  of  his  reviewers  has  noticed  it '.  In  the 
second  place,  he  nowhere  expressly  recoi^nizcs  the 
effects  upon  his  theory  of  evolution,  which  necessarily 
follow  from  the  change.  And,  lastly,  the  manner  in 
which  he  endeavours  to  underpin  that  theory  after 
having  thus  removed  its  logical  foundation  in  his 
former  postulate  of  the  absolute  stability  of  germ- 
plasm,  is  so  peculiar  that  it  is  hard  to  epitomize  his 
reasoning  with  due  regard  to  brevity. 

Speaking  for  myself,  I  can  only  say  that  my  first 
impulse,  after  reading  the  sentences  above  cjuoted, 
was  to  cancel  the  whole  of  Chapter  IV,  as  well  as  all 
those  parts  of  Chapters  I  and  III  where  the  Weis- 
mannian  theory  of  evolution  is  alluded  to  ;  and  then 
to  start  anew  with  a  bare  statement  that  this  theory 
had  now  been  wholly  discarded  by  its  author.  lUit 
after  due  consideration  it  seemed  desirable  to  leave 
the  criticism  as  it  was  originally  written,  not  only  on 
account  of  the  reasons  already  stated  in  the  Preface, 
but  still  more  because  I  found  it  would  be  impractic- 
able to  start  a  new  criticism  of  the  greatly  modified 
theory  of  evolution   without   introducing    many  and 

'  Nature,  May  ii,  pp.  28 -29. — In  1S91-2  I'rofessor  Ilaitog  furnished 
a  criticism  of  Wci^niann's  theory  of  Ilercilily  (A'a/nre,  vol.  44.  p.  613, 
and  ContcuiponD-y  A't't'/cTt',  July,  1S92K  Although  disputed  at  the  time 
by  some  of  W'eismann's  followers  in  luiyland,  this  criticism  was  one  of 
im(|uestionat)le  cogency,  anil  has  now  been  recognized  as  such  hy 
Weismann  himself  ^'Ihe  O'enn-plasiii,  pp.  4,^4:;).  'i'he  main  point  of 
the  criticism  had  been  missed  by  previous  critics  of  \\  eisiuann,  and 
consisted  in  revealing  an  imi)ortant  "difficulty"  inherent  in  the  structure 
of  the  theory  itself.  How  far  this  criticism  had  the  effi  ct  of  causing 
Professor  Weismann  to  abandon  his  theory  of  variation  being  ex- 
clusively due  to  anii)liimixis,  as  Trofessor  Ilartog  appears  to  think 
{Aalurr,  May  11,  li^93,  p.  2S),  is  immaterial.  But  it  must  be  obseived 
that  as  lar  back  as  February,  1S90,  Professor  Weismann  in  his  answer  to 
Professor  Vines'  criticism  wrote  the  passage  already  quoted  on  page  152. 


I 


:'    M 


"'•^wplf^'^^pf^lp' 


156    An  Examination  of  Wcisniannisni. 

Icn^^thy  jiarts  of  the  old  one,  for  the  purpose  of 
shovvinj^  how  the  most  recent  theory  liad  been  arrived 
at.  Mence,  seeing  that  my  previous  criticism  was 
far  from  havinj^  been  rendered  obsolete  by  the  larcje 
clianj^es  which  liad  taken  place  in  Weismann's  system 
of  theories,  I  concluded  that  it  was  best  to  retain 
what  I  had  written,  and  add  the  present  paraf^n-ajihs 
for  the  i)urpose  of  dealing  exclusively  with  the 
changes  in  question. 

In  now  proceeding  to  do  this,  I  think  it  is  needless 
to  occupy  space  by  giving  the  reasons  which  have 
caused  Weismann  thus  to  abandon  his  doctrine  of  the 
universal  stability  of  germ-plasm  since  the  first  origin 
of  sexual  propagation,  and  to  substitute  the  precisely 
opposite  doctrine  of  its  universal  instability.  It  is 
enough  to  say  that  these  reasons  all  arise  by  way 
of  logical  necessity  from  the  further  working  out  in 
TJic  Germ-plasm  of  his  theory  of  heredity — or,  more 
correctly,  from  the  additions  which  he  has  there  made 
to  his  previous  views  on  the  mechanism  of  heredity. 
Thus  he  has  reversed  his  former  doctrine  touching 
the  absolute  stability  of  germ-plasm,  not  so  much 
on  account  of  any  of  the  general  considerations  or 
particular  facts  which  I  have  adduced  against  it  in 
Chapter  IV,  as  because  it  would  not  tally  with  the 
recent  additions  which  he  has  made  to  other  parts 
of  his  system.  Any  one  who  cares  to  follow  this 
matter  will  find  the  reasons  in  question  fully  and 
lucidly  stated  in  Chapter  XIV  of  The  Germ-plasm  ^ 

'  It  is  almost  iiccillcss  to  say  that  no  fault  is  to  be  found  with 
Weismann  for  havini;  thus  reversed  his  opinion  touciiinij  one  of  his 
fundamental  postulates  Consistency  is  no  merit  in  a  m;in  of  science; 
and  least  of  all  where  matters  of  sucii  hii,di  speculation  arc  concerned. 
I  think,  however,  that  it  is  open  to  question  w  hether  an  author  of  any 


IVeisinaiinisni  tip  to  date  (I^>93).       157 


It  is  of  more  inii)()rtancc  to  consider  the  means 
whereby  Weisinann  seeks  to  save  his  theory  of  cvo- 
kition  after  he  has  thus  removed  its  foundation  in  his 


for 


mer  postulate  of  the  absolute  stabih'ty  of  j^erm- 
phism.  A  far  as  1  can  understand,  he  seeks  to  do  so 
as  follows. 

In  the  first  place,  it  must  be  noted  that  after 
his  changes  of  view  with  regard  to  polar  bodies, 
unicellular  organisms,  and  the  significance  01  sexual 
reproduction,  nothing  remains  of  his  original  theory 
of  evolution  save  what  he  can  manage  to  retain  of  his 
original  theory  of  variation  as  due  to  atiii)himi,\is. 
But,  as  we  have  just  seen,  he  has  surrendered  this 
latter  theory  also.  Therefore,  at  first  sigiit  it  appears 
that  no  i)art  of  the  former  can  possibly  remain. 
Beginning  at  the  apex,  he  has  removed,  stone  by 
stone,  his  doctrine  of  descent,  and,  on  arriving  at 
its  fundamental  postulate — the  absolute  stabi''ty  of 
germ-plasm — simply  turns  it  upside  down.  Surely, 
therefore,  it  may  be  thought,  there  is  here  as  complete 
a  destruction  as  well  could  be  of  all  this  side  of 
Weismann's  system.  Such,  however,  he  enileavours 
to  show  is  not  the  case.  He  regards  it  as  still  possible 
to  retain  so  much  of  his  theory  of  descent  as  is 
presented  by  what  he  can  save  of  his  theory  of  vari- 
ation, thus : — 

Although  he  now  represents  that  the  instability  of 

kind  should  suffer  an  cLiljoratc  system  of  thcoiiL-s  to  he  [)ul)lislicd  and 
translated,  at  the  very  time  when  lie  is  himselt  engaged  in  producini; 
another  woriv  siiouinj;  the  untenable  cliaraeter  of  tiicir  basal  premises. 
At  any  rate,  it  would  have  saved  his  Knj;li  h  readers  no  small  trouble 
and  confusion,  if  W'eismann  iiad  added  notes  to  the  translations  of  his 
essays  on  Polar  l^odics,  on  The  Sv^nificiDicc  of  Sexual  Reproduction, 
and  on  AnrphiiiiLxis,  to  tlie  effect  that  lie  had  aixindoned  some  of 
their  most  distinctive  fealuies  before  the  translations  liad  gone  to  press. 


J:.t 


I5<S    y/;/  Exiwii nation  of  ll\isniatinisni. 

I^cnn-plasin  is  such  that  in  no  case  can  ami)himixis 
have  had  aiiythini,^  to  do  with  the  orii!;in  of  congenital 
variations,  he  continues  to  rci^ard  the  stability  of 
^erni-i)lasni  sufficiently  j;rcat  to  necessitate,  in  all 
cases,  the  occurrence  of  amphimixis  in  order  to 
promote  the  (tcvclopntcut  of  conijenital  variations.  In 
other  words,  nolwithstandinj^  that  he  now  thinks  all 
congenital  variations  must  be  het^un  by  external 
conditions  actinij  directly  on  an  unstable  i^erm-plasm, 
he  also  thinks  that  the  amount  of  variation  thus 
[jHuiuced  is  likely  to  be  cxceeilin<^ly  minute,  and 
must  therefore  be  increased  by  subsic[uent  amphi- 
mixis in  order  to  fall  within  the  ransjc  of  natural 
selection.  So  that,  alth()UL,di  powerless  to  initiate 
coni^enital  variation,  amphimixis  must  still  play  an 
indisi)ensal)le  part  in  the  process  of  evolution,  as  in 
all  cases  a  necessary  condition  to  the  occurrence  of 
natural  selection.  External  conditions  first  cause 
slii^ht  chani^es  in  the  determinants  of  a  species  ;  but 
these  are  so  sliL;ht  that  they  have  to  be  augmented  by 
amphimixis  before  they  constitute  material  on  which 
natural  selection  can  act,  and  hence  before  they  can 
become  of  any  significance  either  in  ontogeny  or 
[)hylogeny. 

Such,  I  take  it,  is  what  Professor  Weismann  would 
now  have  us  to  understand  ;  for  otherwise  I  should 
have  expected  from  him  as  frank  a  surrender  of  his 
theory  of  evolution  (or  the  remnant  thereof  in  his 
theory  of  variation)  as  he  has  made  of  its  funda- 
mental postulate.  But,  if  such  is  his  meaning,  I  may 
mention  the  reasons  which  appear  to  me  to  render 
it  nugatory. 

In    the    first    place,    it    is    evident    that     in    thus 


'sin. 


Wi'ismannisin  up  to  dale  (KS93).       159 


ii[)himixis 
:on^cnital 
ability  of 
tc,  in  all 
order  to 
:ions.  In 
thinks  all 

cxtcrn.il 
'm-plasni, 
tion  thus 
nutc,  and 
it  amphi- 
f  natural 
)  initiate 
.  play  an 
ion,  as  in 
rrcnce  of 
"St   cause 

ies  ;  but 
ented  by 
)n  which 

hey  can 

geny   or 

n  would 
should 

r  of  his 
in  his 
funda- 

j,  I  may 

)  render 

in    thus 


niinimi/ini;  the  possible  range  of  congenital  variation 
due  to  the  action  of  external  conditions  on  a  non- 
absolutely  stable  substance  of  hendity,  Weistnann 
is  making  a  wiiolly  gratuitous  a.ssum[)ti{)n,  for  the 
sole  purpose  of  saving  what  remains  of  his  theory 
of  evolution— i.  e.,  the  doctrine  of  the  immense  im- 
portance of  am[)himixis. 

We  have  already  seen  in  the  foregoing  chajiter, 
that  his  original  assumption  of  the  ahsolutc  stabih't)' 
of  germ-plasm  was  a  gratuitous  one,  made  for  the 
pur[)ose  of  suppl\'ing  a  foundation  for  constructing 
his  theory  of  evolution.  lUil  still  more  gratuitous 
is  the  assumption  which  he  has  now  substituted,  for 
the  purjxise  of  saving  as  much  of  this  theory  as 
is  left— the  assum[)tion,  namely,  that  germ-plasm, 
although  universally  unstable,  nevertheless  everywhere 
presents  only  a  certain  low  degree  of  instabilit)-, 
which  serves  to  accommodate  his  modifieil  theory 
of  heredity  on  the  one  hand,  and  all  that  is  jjossible 
of  his  previous  theory  of  evolution  on  the  other.  His 
original  assum[)tion,  ujitenable  though  it  was,  fur- 
nished at  least  a  logical  basis  for  the  necessary  con- 
elusion  that  am[)himixis  v- -.s  the  only  iKXssible  cause 
of  congenital  variations,  liut  there  is  not  so  much  as 
any  logical  sequence  in  the  now  substituted  assuni[)tion, 
that  (A)  all  congenital  variations  are  ultimately  due 
to  the  universal  instability  of  germ-plasm,  and  (H)  that 
nevertheless  they  are  all  more  proximately  due  to  such 
a  liigJi  degree  of  stability  o(  germ-plasm  as  necessitates 
am[)himixis  as  the  only  means  whereby  variations  can 
be  made  "  perceptible."  These  statements  are  as 
independent  of  one  another  as  any  two  statements 
can  well  be  ;  and,  therelore,  if  the  second  of  them  is  to 


i6o    An  Exaudfiation  of  Weismannism. 


\i 


:3 


Pi!    i 


]'P!  i 


ill) 


be  substantiated,  it  can  only  be  so  by  some  totally 
distinct  line  of  reasoning  The  first  statement  does  not 
even  tend  to  suggest  the  second  ;  ni  fact  it  tends  to 
suggest  the  precise  contrary.  For,  obviously,  there  is 
nothing  in  the  logic  of  the  matter  to  show  why,  if 
all  congenital  variations  depend  for  their  origin  on 
the  instability  of  germ-plasm,  such  instability  must 
nevertheless  be  always  so  slight  that  the  variations 
due  to  it  must  afterwards  depend  on  amphimixis  for 
their  devchjpment  to  the  point  where  they  become 
"perceptible."  As  above  indicated,  it  is  surely  little 
short  of  absurd  thus  to  assume  that  a  universally 
unstable  germ-plasm  universally  presents  only  that 
particular  degree  of  instability  which  will  serve  to 
accommodate  Professor  Weismann's  newer  theory  of 
heredity,  and  at  the  same  time  to  save  thus  much 
of  hiS  previous  theory  of  evolution. 

But  now,  in  the  second  place,  not  only  is  this 
assumption  wholly  gratuitous,  but  there  are  many 
considerations  which  render  it  in  the  highest  degree 
improbable,  while  there  ai^  not  wanting  facts  which 
appear  to  demonstrate  that  it  is  false.  For.  unquestion- 
ably, most  of  the  considerations  which  have  already 
been  advanced  in  the  preceding  chapter  against  the 
assumption  of  an  absolute  stability  of  germ-plasm,  are 
here  equally  available  against  the  assumption  of  an 
imperceptibly  small  amount  of  instability  ^  Similarly, 
all  the  facts  thcie  given  with  regard  to  the  a-sexual 
origin    of    species — and   even    genera — of    partheno- 

'  See  especially  pp  86-89.    All  thnt  is  there  said  about  the  unicellular 

organisms  is   not,  'n   the   jiresmt   connexion,  affecteil   by  Weismann's 

;hange  of  view   with    ic^ard  tu   thcin.     \\'e  have   only   to   substitute 

'primonliril"  or  "protoplasmic''  lor  "unicellular,"  and  ncaily  all  the 

points  ol  the  ciilicisni  remain. 


m. 

ic  totally 
;  does  not 

tends  to 
T^  there  is 
V  why,  if 
oriLrin  on 
lity  must 
i^ariations 
imixis  for 
7  become 
rely  little 
nivcrsally 
only  that 

serve  to 
theory  of 
us    much 

/   is  this 

re    many 

t  degree 

s  which 

uestion- 

al  ready 

linst  the 

ism,  are 

)n  of  an 

milarly, 

a-sexual 

arthcno- 

unicellular 
Vcisnmnn's 

substitute 
uly  all  the 


Weisniannisfu  itp  to  date  (1893).       i6t 

genetic  organisms,  bud-variation  ^,  &c.,  amply  de- 
monstrate that  congenital  variations  due  to  the 
instability  of  germ -plasm  alone,  or  apart  from  amphi- 
mixis, are  somc'imcs  enormous.  Hence,  we  cannot 
accept  the  gratuitous  suggestion  that  in  all  other 
cases  they  arc  100  insignificant  to  count  for  anything 
till  they  have  been  augmented  by  amphimixis,  even 
although  we  may  be  prepared  to  agree  tha:  amphi- 
mixis is  probably  one  important  factor  in  Uie  pro- 
duction of  congenital  variations.  What  degree  of 
importance  it  presents  in  this  connexion,  however, 
we  have  not  at  present  any  means  of  determining  ; 
all  we  can  conclude  with  certainty  is,  that  in  some 
cases  it  is  demonstrably  ve/y  much  less  than  Weis- 
mann  supposes,  while  it  is  extremely  improbable  that 
it  is  ever  in  any  case  the  sole  and  necessary  antecedent 
to  the  operation  of  natural  selection. 

This  extreme  improbability  is  shown,  not  only  by 
what  I  have  already  .said  in  the  previous  chapter,  and 
need  not  here  repeat  ;  but  likewise  by  the  *'  sever-\l 
considerations  "  which  Darwin  has  adduced  with 
regard  to  this  very  point,  aivl  which,  as  he  says, 
"alone  render  it  probabJe  that  variability  of  every 
kind  is  directly  or  indirectly  caused  by  changed 
conditions  of  lite,"  with  the  con.sequence  that  "tho.se 
authors  who  attribute  all  variability  to  the  mere  act 
of  sexual  union  are  in  error."  I  have  already  quoted 
tliL  ic  words  further  back  in  the  [jresent  chapter,  in 
order   to  show   that   by   now   attributing  the  origin 

'  Professor  Weismaiin  has  now  considered  more  fully  than  heretofore 
the  phenomena  of  bud-variation  '  7'/u  Ucrm-plasin,  i)p.  439-442) ;  but 
as  he  continues  (though  witli  diffidcncL')  to  lake  substantially  the  same 
\iew  of  tiiem  as  that  which  I  have  already  ([Uuted  on  pp.  y^  -y6,  it  is 
needless  fur  nic  to  rc-discuss  (he  m.attcr  hii'j. 

M 


1 62    Ah  Examination  of  Wcismanmsin. 


I| 


of  all  conc^cnital  variations  to  the  direct  action  of 
external  conditions.  Weismann  has  brought  himself 
into  line  with  Darwin  so  far  as  this  fundamental 
point  of  doctrine  is  concerned.  But  I  here  re-quote 
the  words  in  order  to  show  that  by  further  attributing 
the  development  of  congenital  variations  •'  to  the  mere 
act  of  sexual  union,"  Weismann  is  again  falling  out 
of  line  with  Darwin.  So  to  speak,  he  first  performs 
a  right-about-fiiCe  movement  as  regards  his  original 
position  towards  the  '•  stability  of  germ-plasm,"  and 
immediately  afterwards  makes  a  half-turn  back  again. 
Now,  it  is  this  half-turn  to  which  I  object  as  un- 
warranted in  logic  and  opposed  to  fact. 

In  a  previous  chapter  (pp.  66-j)  I  presented  to  him 
the  dilemma,  that  germ-[)lasm  must  be  either  ab- 
.soUitely  stable  or  else  but  highly  stable,  and  that  in 
the  former  case  his  theory  of  amphimixis  as  the  sole 
cause  of  congenital  variations  would  be  valid,  while 
in  the  latter  case  the  theory  would  collapse.  But  it 
did  not  then  occur  to  me  that  Weismann  might  seek 
a  narrow  seat  between  the  horns  of  this  dilemma,  by 
representing  that  germ-plasm  is  universally  unstable 
up  to  a  certain  very  low  degree  of  instability — viz., 
exactly  that  degree  which  is  required  for  starting 
a  congenital  variation  by  means  of  external  causes, 
without  its  being  possible  for  the  variation  to  become 
perceptible  unless  afterwards  incn.^sed  by  means  of 
amphimixis.  And  now  that  this  extremely  sophis- 
tical position  has  been  adopted,  I  cannot  see  any 
imaginable  reason  for  adopting  it  other  than  a  la.-it 
endeav  ir  to  .save  as  much  as  possible  of  his  former 
theory  of  evolution.  There  can  be  nothing  in  the 
nature  of  things  thus  to  limit,  within  the  narrowest 


iVPI 


:tion  of 
himself 
amcntal 
•e-quote 
ributing 
he  mere 
ling  out 
)erforms 
original 
m,"'  and 
;k  again. 
:  as   Lin- 


Weisffiannism  tip  to  date  (1893).       1^3 

possible  range,  the  instability  of  a  universally  unstable 
germ-plasm — distributed,  as  this  most  complex  of 
known  substances  is.  throughout  all  species  of  plants 
and  animals,  and  exposed  to  inconceivably  varied 
conditions  of  life  in  all  quarters  of  the  globe.  And 
these  considerations  are  surely  of  themselves  enough 
to  dispose  of  the  assumi)tion  as  absurd,  without  again 
rehearsirg  the  facts  of  congenital  variation  which 
definitely  prove  ii  to  be  false. 


1  to  him 

;her   ab- 

i  that  in 

the  sole 

d,  while 

But  it 

ht  seek 

nma,  by 

unstable 

;y— viz., 

starting 

causes, 

become 

leans  of 

sophis- 

ice  any 

a  la^t 

former 

in  the 

rrowest 


Conchisioii. 

For  reasons  stated  at  the  commencement  of  this 
chapter,  I  have  restricted  its  subject-matter  almost 
exclusively  to  a  consideration  of  the  more  fundamental 
changes  which  Professor  Weismann  has  wrought  in 
his  general  system  of  theories  by  the  publication  of 
his  most  recent  works.  In  other  words,  I  have  pur- 
posely avoided  considering  those  inmiensely  elaborate 
additions  to  his  theory  of  heredity  which  constitute 
by  far  the  largest  portion  of  his  essays  on  AmpJiiuiixii 
and  The  Gcnn-plasin,  and  which  have  {or  their  object 
an  ideal  construction  of  "  the  architecture  of  germ- 
plasm." 

The  fundamental  changes  to  which  allusion  has 
just  been  made  are  as  follows. 

Professor  Weismann  has  to  a  large  extent  abandoned 
his  theory  of  polar  bodies,  and  in  my  opinion  would 

M  2 


;  ■  • '    1 


t    -Tw 


164    All  Examinatio7i  of  Weismannism. 

have  done  well  had  he  taken  a  further  step  and 
surrendered  the  theory  in  toto. 

Similarly,  he  has  withdrawn  his  previous  distinctions 
between  the  unicellular  and  multicellular  organisms. 
The  Protozoa  and  Protophyta  are  now  included  by 
him  in  the  same  category  as  the  Meta/.oa  and  Meta- 
[)hyta,  as  regards  all  matters  of  individual  variation, 
reproduction,  subjection  to  the  law  of  natural  selection, 
and  so  forth.  The  only  difference  which  he  continues 
to  allege  is  the  somewhat  metai)hysical  one  touching 
mortality  and  imiuortality.  Ikit  I  have  given  what 
appears  to  me  sufficiently  good  reasons  for  ignoring 
this  distinction  ;  and  therefore,  as  it  seems  to  me, 
everyone  of  Weisniann's  previous  doctrines  respecting 
unicellular  organisms  have  vanished — very  much  to 
the  benefit  of  his  system  as  a  whole. 

By  far  the  greatest  change,  however,  which  he  has 
made  in  this  general  s}stem  is  that  which  he  has 
effected  by  surrendering  the  postulate  of  the  absolute 
stability  of  germ-plasm.  The  rift  in  his  lute  which 
has  been  noticed  with  regard  to  this  matter  lias 
now  been  widened  to  an  extent  which  docs  prevent 
any  further  harping  on  the  theme  of  evolution.  It 
is  true  that  Weismann  endeavours  to  retain  as  far  as 
possible  the  general  character  of  his  former  postulate 
of  the  universal  stability  of  germ-plasm,  with  the 
consecjuent  ''  significance  of  sexual  reproduction  "  as 
the  sole  cause  of  congenital  variation.  For  although 
he  now  reverses  both  these  doctrines  by  saying  that 
germ-i)lasm  is  universally  unstable,  and  that  sexual 
reproduction  is  in  no  case  the  sole  cause  of  congenital 
variation,  he  seeks  at  the  same  time  to  minimize  tht 
logical  consequences  of  such  reversal  by  making  ar 


MiT 


Weismannis7u  up  to  date  (1893).       165 


what 


that 
lexLial 
Icnital 

ie  tht 


ingenious  assumption,  the  possilDiHty  of  which  I  had 
not  foreseen  when  writing  the  previous  chapters. 
The  assumption  is,  that  altliough  germ-plasm  is 
universally  unstable,  the  degree  of  its  instability  is 
everywhere  restricted  within  the  narrowest  possible 
limits  ;  so  that  sexual  propagr^  'on  is  still  necessary 
for  the  purpose  of  developing  congenital  variations  to 
the  point  where  they  can  fall  within  the  range  of 
natural  selection,  notwithstanding  that  they  must  all 
have  been  originated  by  external  causes  acting 
directly  on  a  germ-plasm  universally  unstable  within 
the  narrow  limits  assumed.  But  clearly  this  as- 
sumption is  arbitrary  to  the  last  degree,  and,  no  less 
clearly,  it  is  made  by  Weismann  for  the  sole  purpose 
of  saving  as  much  as  he  can  of  his  previ(^us  theory  of 
variation.  His  more  recent  speculations  touching 
the  mechanism  of  heredity  arc  incompatible  with  his 
former  view  of  amphimixis  as  the  sole  cause  of  con- 
genital variations,  and  therefore  he  makes  this  arbitrary 
assumption  for  the  purpose  of  representing  that  am- 
phimixis may  nevertheless  still  be  regarded  as 
a  necessary  con-cause.  I  need  not  here  repeat  what 
has  .so  recently  been  said  touching  the  sophistry  of  this 
assumption  in  theory,  or  the  demonstrable  falsity  of  it 
in  fact,  it  is  enough  to  remark,  in  conclusion,  that 
the  game  is  not  worth  the  candle.  It  was  originally 
well  worth  Weismann's  while  to  sustain  his  funda- 
mental postulate  of  the  absolute  stability  of  gcrm- 
nlasm,  because  he  was  al)le  to  re; 


>P 


theory  of  evolution.  lUit  tlie  only  part  of  this  theory 
which  he  has  now  left  standing,  or  which  he  can  now 
save  by  his  newer  postulate  of  a  germ-])lasm  both  stable 
and   unstable   at  the    same  time,    is    his    doctrine  o^ 


# 


W' 


1 66    An  Examination  of  Weisniannism. 


variation.  So  to  speak,  it  is  his  desire  to  reserve  as 
much  as  is  speculatively  possible  from  the  general 
ruin  of  his  theory  of  descent,  that  causes  him  to  go  so 
far  to  attempt  so  little.  For  I  cannot  si  jpose  that  he 
himself  will  expect  any  of  his  readers  to  entertain 
so  arbitrary,  fanciful,  and  demonstrably  false  an 
assumption  as  the  one  in  question.  Surely  it  would 
have  been  better  to  have  surrendered  in  toto  this 
*'  Weismannian  theory  of  variation,"'  rather  than  to 
have  attempted  its  rescue  by  means  so  plainly 
nugatory.  It  might  still  have  been  held  that  ami)hi- 
niixis  plays  a  large  and  important  part  as  one  of  the 
causes  of  variation,  and  therefore  also  as  one  of  the 
factors  of  organic  evolution.  After  having  reversed 
his  postulate  of  amphimixis  being  the  sole  cause  of 
variability,  and  therefore  having  agreed  with  Darwin 
that  "  those  writers  are  in  error  who  attribute  all 
variability  to  the  mere  act  of  sexual  union,"  he  might 
well  have  questioned  Darwin's  further  statement  as  to 
its  being  "  probable  that  variability  of  every  kind  is 
directly  or  indirectly  caused  by  changed  conditions 
of  life."  But  by  now  assuming  that  variations  due  to 
any  causes  other  than  amphimixis  must  be  '•  imper- 
ceptible "  until  they  have  been  augmented  by  amphi- 
mixis, Weismann  is  shutting  out,  with  a  futile  hypo- 
thesi.s,  the  important  question  as  to  whether,  or  how 
far,  amphimixis  really  is  a  cause  of  variation.  Observe, 
the  case  is  not  as  it  might  have  been  were  there  no 
reasons  assignable  for  the  occurrence  of  sexual  pro- 
pagation, other  than  that  of  assisting  in  the  production 
of  congenital  variaticnis.  The  theory  of  "  rejuve- 
nescence," for  example,  i^  prima  faci  •  a  more  probable 
one  than  that  which  ascribes  to  sexual  propagation 


H  :l'i 


m. 

eserve  as 
:  general 
to  go  so 
e  that  he 
entertain 
false  an 
it  would 
toto  this 
than   to 

plainly 
t  amphi- 
ne  of  the 
)e  of  the 
reversed 
cause  of 
I  Darwin 
ibute  all 
le  might 
ent  as  to 
r  kind  is 
auditions 
IS  due  to 

impcr- 
r  am  phi - 
c  hypo- 

or  how 
Observe, 
there  no 
ual  pro- 
xluction 

rejuve- 
)robable 
,)agation 


Wcismannism  itp  to  date  (1893).        167 

the  function  of  causing  variability  '  ;  while  Galton's 
hypothesis,  which  supposes  the  object  of  this  form  of 
propagation  to  be  that  of  conserving  the  "  germs  " 
(  =  "  determinants ")  of  the  phyla,  has  a  good  deal 
to  say  for  itself-.     Of  course  such  alternative  hypo- 


'  "  l^eiuvenescence ' 


means  the  rencwnl  of  vital  enerijies  which  is 
supposed  to  result  from  a  fusion  of  tlic  contents  of  two  cilis.  For  an 
excellent  discussion  of  this  and  the  other  theories  on  the  object  of  sexual 
propagation,  see  a  brief  article  by  Professor  Marcus  Hartog,  in  the 
Contemporary  Rcvieiv  for  July,  i  S92.  vSince  then  Weismann  has  pul>lished 
The  Germ-plasm,  and  here  his  main  argument  against  this  theory  is  that 
tens,  or  even  hundreds  of  generations  of  unicellular  organisms  have  l)ec'n 
observed  to  succeed  one  anotlier  before  any  act  of  conjugation  takes 
jilace.  Hut  I  cannot  see  that  it  signifies  how  many  generations  may  in 
different  species  be  jiroved  capaMe  of  resulting  from  a  single  act  of  con- 
jugation. Weismann  himself  now  accepts  the  analogy  between  cell- 
proliferation  as  resulting  from  conjugation  in  unicellular  organisms,  and 
from  fertilization  in  multicellular.  But  even  three  hundred  generations 
of  the  former  can  scarcely  be  regarded  as  equal  to  all  the  "  ontogenetic 
stages  "  of  the  latter. 

'*  This  view  of  the  function  of  sexual  propagation  is  now  universally 
ascribed  to  Strasburger,  and  it  is  quite  true  that  he  has  indeiKiidently 
adduced  it.  Ikit  as  this  was  not  done  until  about  ti  n  years  afiti  it  iiad  been 
published  byGalton,  I  have  designedly  associated  the  idea  with  Galton's 
name.  The  following  are  the  words  in  which  it  was  announced 
by  him : — 

"The  necessity  of  a  system  of  double  parentage  in  complex  organisa- 
tions is  the  immediate  consequence  of  a  tlieory  of  organic  units  niid 
gcims,  as  we  shall  see  if  ue  lix  oUI  attention  u|>on  any  one  definite  series 
of  unisexual  descents,  and  follow  out  its  historj'.  Suppose  we  select, 
cut  off,  and  plant  the  second  bud.  then  after  it  has  grow n  to  niatmity  we 
similarly  take  the  secom'  of  its  buds,  and  so  on  consecutively.  At  each 
successive  stage  tiicre  is  aluajs  a  chance  of  some  one  or  more  of  the 
various  species  of  germs  ii^  the  slirp  dying  out,  or  being  omitted;  and  of 
course  when  they  are  gunrlhtyare  lost  for  ever,  and  arc  irreplaceable 
jjy  others.  From  time  to  time  this  chance  must  fall  unfavcniraljlj .  an<l 
will  cause  a  deficiency  in  some  of  the  structural  elements,  and  a  consc 
quenl  deterioration  of  the  race.  If  the  loss  be  vital,  this  particular  line 
of  descent  will  of  course  be  extinguished  at  once  ;  but  on  tiie  more 
favourable  supposition,  the  race  will  linger  on,  submitting  to  successive 
decrements  in  its  constituent  elements,  until  the  accumulation  of  small 
'osses  becomes  latal." — loc.  cit..  \>.  3.^.',. 

(jalton    also    p(jints     out    a    further   advantage   that   is   secured    by 


1 68    An  Examination  of  Weismannisvi. 


r- 


\M 


theses  touching  "the  significance  of  sexual  repro- 
duction "  are  not  necessarily  exclusive  of  one  another  : 
the  process  may  subserve  two  or  more  adaptive 
purposes  ^  But  he  would  be  a  bold  man  who,  in  the 
present  state  of  our  knowledge,  could  accept  unre- 
servedly the  particular  view  of  this  process  which 
Darwin  so  emphatically  rejected ;  and  I  think  he 
must  be  a  biased  man  who  could  entertain  for 
an  instant  the  modification  of  this  view  which  Wcis- 
mann  has  now  substituted. 

Thus,  the  Wejsmannian  theory  of  evolution  has 
entirely  fallen  to  pieces  with  the  removal  of  its 
fundamental  postulate — the  absolute  stability  of 
germ-plasm.  It  only  remains  to  mention  once  more 
the  effects  of  this  removal  upon  the  other  side  of  his 
system — viz.,  the  companion  postulate  of  the  uninter- 
rupted continuity  of  germ-plasm,  with  its  superstructure 
in  his  theory  of  heredity. 

Briefly,  these  effects  are  as  follows  : — 

I.  Germ-plasm  ceases  to  be  continuous  in  the 
sense  of  having   borne   a  perpetual    record   of  con- 

"  amphimixis,"  and  one  which  shows  the  non-necessity  of  what  remains 
of  Wfismann's  theory  of  polar  bodies,  thus — 

"  Tiiere  is  yet  another  advaiitaj^e  in  double  parentnc^c,  namely,  that  as 
the  stirp  whence  the  child  sijrang  can  only  be  half  the  size  of  the 
combined  stirps  of  his  two  parents,  it  follows  that  one  half  of  his  possible 
heritage  must  have  been  suppressed.  Tiiis  implies  a  sharp  struijgle  for 
place  among  the  competing  germs,  and  the  success,  as  we  may  infer, 
of  the  fitter  half  of  their  numerous  varieties." — loc.  cit.,  p.  334. 

'  In  fact,  it  seems  to  me  that  this  is  the  sole  supposition  whereby  it 
can  be  held  that  sexual  propagation  has  bten  developed  both  " /rj' "  and 
'^for'"  natural  selection,  in  order  to  supply  variations  as  material  for  the 
action  of  this  priiiciple.  Natural  selection  cannot  thus  supply  tlie 
conditions  to  its  own  activity,  if,  as  Weismann  supposes,  there  is  but 
one  purpose  for  it  to  subserve  (see  above,  pp.  13-15).  liut,  if  it 
is  acting  for  more  than  one  purpose,  the  "  by  "  and  the  "  for"  argument 
may  hold. 


con- 

rcniains 

that  as 

of  the 

)ossiblc 

;j,'le  lor 

ay  infer, 

ereby  it 

by  "  and 
for  tlie 
jly    tlic 

e  is  but 
,    if  it 

rgument 


Weismaitnism  np  to  date  (189;^).       169 

genital    variations    from    the    first    origin    of   sexual 
propagation. 

2.  On  the  contrary,  as  all  such  variations  have 
been  originated  by  the  direct  action  of  external 
conditions,  the  continuity  of  germ-plasm  in  this  sense 
has  been  interrupted  at  the  commencement  of  every 
inherited  change  during  the  phylogcny  of  all  plants 
and  animals,  unicellular  as  well  as  multicellular. 

3.  But  germ-plasm  remains  continuous  in  the 
restricted,  though  still  highly  important  sense,  of 
being  the  sole  repository  of  hereditary  characters  of 
each  .successive  generation,  so  that  accpu'red  characters 
can  never  have  been  transmitted  to  progeny  "  repre- 
sentatively," even  although  they  have  frequently 
caused  those  "  specialized  "  changes  in  the  structure 
of  germ-plasm  which,  as  we  have  .seen,  must  certainly 
have  been  of  considerable  importance  in  the  history 
of  organic  evolution. 

4.  By  surrendering  his  doctrine  of  the  absolute  ^ 
stability  of  germ-plasm  on  the  one  hand,  and  of  its 
perpetual^  continuity  on  the  other,  Weismann  has 
greatly  improved  his  theory  of  heredity.  For,  what- 
ever may  be  thought  of  his  recent  additions  to  this 
theory  in  the  way  of  elaborate  speculation  touching 

*  I  find  that  a  passage  cxjdainiiif,^  il;j  sense  in  wliicli  1  use  these  leims 
has  been  accidentally  omitteil  from  Chajiter  III,  wliere  tliey  are  first 
introduced  ;  and,  as  the  sheets  of  that  chapter  have  been  already  printed 
off,  I  here  supply  the  omission.  The  terms  in  italics  are  not  Weismaim's, 
and  I  have  employed  them  merely  for  tiie  purjiose  ot  gi\iiii^  i)recision  to 
his  views.  By  "  absohtte  stability  of  j,'erm-plasm  "  I  mean  to  indicate 
that  degree  of  stability  which  he  has  hillierto  postulated  as  the  necessary 
basis  for  his  doctrine  of  heritable  variations  beinj^^  solel}-  due  to  admix 
tures  of  germ-plasm  in  sexual  uiuons.  15y  "■perpetual  continuity  of 
germ-plasm"  I  intend  to  denote  that  amount  of  continuity  wiiich  he  still 
postulates  as  the  neccssar)  basis  for  his  correlative  doctrine  touching  the 
non-inheritance  of  acquired  characters. 


m 


w 


i   i 


IF 


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^ 

^.''                               ' 

i\ 

1 70    An  Examination  of  IVcisnianiiism. 

the  ultimate  mechanism  of  heredity,  it  is  a  great 
gain  to  have  freed  his  fundamental  postulate  of  the 
continuity  of  germ-plasm  from  the  two  further 
postulates  which  have  just  been  mentioned,  and  the 
sole  purpose  of  which  was  to  provide  a  basis  for  his 
untenable  theory  of  evolution. 

5.  In  my  opinion  it  only  remains  for  him  to 
withdraw  the  last  remnant  of  his  theory  of  evolution 
by  cancelling  his  modified  and  even  less  tenable 
views  on  amphimixis,  in  order  to  give  us  a  theory  of 
heredity  which  is  at  once  logically  intact  and  bio- 
logically probable. 

6.  The  theory  of  germ-plasm  would  then  resemble 
that  of  stirp  in  all  points  of  fundamental  importance, 
save  that  while  the  latter  leaves  the  question  open  as 
to  whether  acquired  characters  are  ever  inherited  in 
any  degree,  the  former  would  dogmatically  close  it, 
chiefly  on  the  grounds  which  I  have  considered  in 
Appendix  II.  It  seems  to  me  that  in  the  present 
state  of  our  knowledge  it  is  more  prudent  to  follow 
Galton  in  suspending  our  judgement  with  regard  to 
this  (juestion,  until  time  shall  have  been  allowed  for 
answering  it  by  the  inductive  methods  of  observation 
and  exi)erimeiit. 

7.  Hence,  in  conclusion,  we  have  for  the  present 
only  to  repeat  what  VVeismann  himself  has  said  in 
one  of  the  wisest  of  his  utterances,—"  The  question 
as  to  the  inheritance  of  acquired  characters  remains, 
whether  the  theory  of  germ-plasm  be  accepted  or 
rejected."        '    " 

It  is  now  close  upon  twenty  years  that  I  accepted 
the  substance  of  this  theory  under  the  name  of  stirp  ; 
and  since  that  time  the  question  as  to  the  inheritance 


IVetsmanmsm  np  to  date  (189;,).       171 

of  acquired  characters  remains  exactly  where  it  was. 
No  new  facts,  and  no  new  considerations  of  much 
importance,  have  been  fortlicominj;  to  assist  us  in 
answering  it.  Therefore,  as  already  stated  in  the 
Preface,  I  intend  to  deal  with  this  question  hereafter 
as  a  question  per  sc.  or  one  which  is  not  specially 
associated  with  the  labours  of  Professor  VVeismann. 


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APPENDIX    I : 

ON    GliKM-l'LASM. 

As  alnaily  slated  in  the  text  (p.  71),  Wcisinann's  j^iiicral 
reasoning  in  suppoil  of  liis  own  theory  of  germ-plasm,  as 
against  Darwin's  theory  of  genmiules  in  any  lonn,  aihnits 
of  being  reduced  to  arguments  in  iavour  of  three  proi)osi- 
tions — viz.,  first,  tiiat  there  is  no  evidence  of  liie  transmission 
of  somatogenetic  cliaractcrs ;  secondly,  dial  the  theory  of  i)an- 
gcnesis,  which  seeks  to  explain  tlu'ir  sujtposed  transmission, 
is  "inconceivable";  and,  thirdly,  that  its  logical  antithesis  — 
the  theory  of  germ-plasm — is  so  nuu  h  less  beset  with 
difliculiies,  that  by  comparison  it  is  simple,  self-coherent, 
and  otVers  a  real,  as  liistinguished  Irom  a  "  formal,"  ex- 
planation of  the  facts  of  hereility. 

I'he  first  of  these  propositions  will  be  discussed  at  con- 
siderable length  in  my  next  volume.  The  second  and  ihirtl 
propositions,  however,  may  be  ilealt  with  here. 

The  following  paragiaph,  whii  h  I  sh.dl  (juote  sentence 
by  sentence,  sets  forth  the  grounds  on  which  W'eismaiin  bases 
the  sccon('  proposition,  namely,  that  any  theory  belonging 
to  the  order  of  pangenesis — i.e.,  which  sujiposes  the  carriers 
of  heredity  ever  to  travel  centripelally — i.'-.,  from  its  very 
nature,  inconceivable. 


At  first  sight  this  hypothesis  seems  to  be  quite  reasonable. 
It  is  not  only  coneeivable  thai  jjarticles  mighl  proceed  bom  the 
iouiatic  to  the  reproductive  cells,  but  the  very  nutrition  v{  the 


174    ^^^^  Examination  of  Wcisnianmsm, 

latter  at  the  expense  of  the  former  is  a  demonstration  t^  it  such 
a  passajje  actually  takes  place.  IJut  a  closer  examination  reveals 
immense  difficuKfCS.  In  the  first  place,  the  molecules  of  the 
body  devoured  are  never  simi)ly  added  to  those  of  the  fcedinj,' 
ind'  idual  without. underj^oin^  any  chanj,";,  but,  as  far  as  we 
k.iow,  they  are  really  assimilated,  that  is,  converted  into  the 
molecules  of  the  latter.  We  cannot  therefore  gain  much  by 
assuming'  that  a  number  of  molecules  can  pass  from  the  },Towing 
somatic  cells  into  the  growing  reproductive  cells,  and  can  be 
deposited  unchanged  in  the  latter,  so  that,  at  their  next  division, 
the  molecules  are  separated  to  become  the  somatic  cells  of  the 
following  generation  '. 

The  obvious  answer  to  this  is.  that  no  one  has  ever 
supposed  "gemmulcs"  to  be  merely  "■molecules"  in  the 
chemical  sense  of  this  word  ;  nor  has  any  one  ever  imagined 
that  they  are  ^'devoured"  by  the  germ-cells  into  which  they 
pass.  Of  course,  if  this  were  the  case — i.e.,  if  genimules  serve 
merely  as/ood  to  the  germ-cells — they  wouhl  become  disin- 
tegrated down  even  to  their  chemically  molecular  structure, 
and  there  would  be  an  end  of  them  as  organized  "  carriers 
of  heredity." 

In  the  second  place,  it  is  askul : — 

I  low  can  such  a  process  \\.e.  the  passage  of  geinmules  into 
growing  germ-cells |  be  conceivable,  when  the  colony  becomes 
more  complex,  when  the  number  of  somatic  cells  becomes  so 
large  that  they  surround  the  reproductive  cells  with  many 
layers,  and  when  at  the  same  time,  by  an  increasing  division 
of  labour,  a  great  number  of  different  tissues  and  cells  are 
produced,  all  ot  which  must  originate  de  novo  from  a  single 
reproductive  cell  ? 

Hero,  again,  the  obvious  answer  is,  lliat  no  one  has  ever 
propounded  such  a  staienieiil.  Far  froin  supposing  that 
"  all  the  iliflferent  cells  and  tissues  of  a  complex  organism 

'  /Assays,  pp.  76-77,  from  which  the  following  tiuotations  are  likewise 
taken  seriaiim. 


Appendix  I. 


175 


must  orii^inate  de  novo  from  a  siv.gle  reproiluctive  cell,"  the 
theory  of  pangenesis  sui),)Oses  the  very  contrary — viz.,  thai 
somatic  clumges  in  the  past  history  of  the  phyla  have  not 
thus  originated  in  any  reproductive  cell.  The  idea  of 
somatic  changes  originating  in  reproductive  cells  belongs 
to  the  theory  of  gcrjn-plas?n ;  but  even  this  theory  does 
not  suppose  all  the  great  number  of  different  cells  and 
tissues  which  compose  a  complex  organism  to  have  ever 
originatetl  de  novo  from  a  single  reproductive  cell. 

The  difficulty  touching  germ-cells  becoming  isolated,  or 
buried,  by  the  phylogcuetic  increase  of  somatic  cells,  is 
enforced  in  the   immediately  succeeding  sentences,  thus: — 

Each  of  these  various  elements  [somatic  cells]  must,  ex 
hypothesis  give  up  certain  molecules  to  the  reproductive  cells; 
hence  those  which  are  in  immediate  contact  with  the  latter 
would  obviously  possess  an  ailvantage  over  those  which  are 
more  remote.  If,  then,  any  somatic  cell  must  send  the  same 
number  of  molecules  to  each  reproductive  cell ',  we  are  compelled 
to  suspend  all  known  pliysical  and  physiological  conceptions, 
and  must  make  the  entirely  gratuit"us  assumption  of  an  affinity 
on  the  part  of  the  molecules  for  tlie  reproductive  cells.  Even  if 
we  admit  the  existence  of  this  aflinity,  its  origin  and  means  of 
control  remain  perfectly  unintelligil)le  if  we  suppose  that  it  has 
arisen  trom  differentiation  of  the  complete  colony.  An  unknown 
controlling  force  must  be  added  to  this  mysterious  anungement, 
in  order  to  marshal  the  molecules  which  enter  the  rejjp  auctive 
cell  in  such  a  manner  that  their  arningement  corresponds  with 
the  order  in  which  they  must  emerge  as  cells  at  a  later  period. 

Now  I  do  not  see  much  force  in  the  s'jggestion  that 
those  somatic  cells  which  happen  to  be  in  immeiliate  con- 
tact with  germ-cells,  "  must  obviously  possess  an  advantage 


'  "  Or,  more  precisely,  they  must  give  up  as  many  molecules  as  would 
correspond  to  the  lunnlK-r  of  the  kind  of  cell  in  (|uesiion  found  in  the 
mature  ortjanism."  Of  course  Ijy  "molecules"  Wcismaim  means  what 
Darwin  does  by  "gcmmules." 


1 76    An  Examination  of  Weismannism. 

ovcT  those  which  are  more  remote."  On  the  contniry,  I 
do  not  see  that  mere  proximity  of  one  species  of  cell  to 
another  species  witliin  ihe  same  organism  need  have  any- 
thing to  do  with  the  matter— still  less  that  "  we  must 
suspend  all  physical  and  physiological  conceptions,"  if  we 
demur  to  the  statement  that  it  "  obviously  must."  As  for 
''physical  conceptions,"  how  many  thousands  of  cases  might 
not  be  pointed  to  among  chemical  and  mechanical  pro- 
cesses where  contact  or  proximity  are  conilitions  of  com- 
paratively little  importance?  And  as  for  "physiological 
conceptions, '  do  we  find  that  any  part  of  the  organism  is 
affected  by  its  distance,  say,  from  the  liver  and  kidneys, 
for  getting  rid  of  its  effete  protlucts?  Is  it  not  rather  the 
case  that  every  gland  in  the  body  is  wholly  unaffected  by 
its  distance  from  any  part  of  the  body,  in  regard  to  its 
function  of  draining  off  the  particular  substances  with  which 
it  is  concerned?  Why  then  should  the  reproductive  gland 
constitute  a  conspicuous  exception?  Or  how  do  we  sus- 
l)cnd  all  physiological  conceptions,  if  we  suppose  that  this 
gland  resembles  every  other  gland  in  being  specialized  to 
secrete  a  particular  kind  of  '•  molecule,"  which,  because  thus 
sjjecially  sdecicd,  may  l)e  said  to  have  for  that  gland  a 
special  "affniity"?  If  there  are  such  things  as  gemmules, 
1  do  not  see  any  violation  t)f  physic>logical  analogies — still 
less  an  "  entirely  gratuitous  assumption " — in  supposing 
that  they  can  be  filtjretl  out  from  all  parts  of  the  body  by 
the  sexual  glands,  and  there  aggregateil  as  a  special  product 
to  be  discharged  in  the  form  of  sexual  elements'. 


'  If  tlicre  arc  such  lliiiif^s  as  yciimiules,  it  appears  to  me  to  follow 
that  the  only  physiological  (li»tinctioii  between  the  leproiluctive  inlands 
and  ylanils  in  general  is,  that  the  former  discharge  their  products  in  the 
form  of  living  cells.  Even  here,  however,  there  appears  to  be  one 
analogous  case  in  those  salivary  glands  which  di^charge  the  so-called 
salivary  corpuscles — i.e.,  nucleated  cells,  undergoing  amoeboid  changes 
of  form,  and  exhibiting  the  movements  of  living  protoplasm  in  their 
interior. 


Appendix  /. 


177 


But,  it  is  further  represented,  "even  if  wc  admit  the 
existence  of  this  aflinity,  an  unknown  controlling  force 
must  be  added  to  this  mysterious  arnmgemcnt,  in  order 
to  marshal  the  molecules  wliieh  enter  the  [growing]  repro- 
ductive cell  in  such  a  manner  that  their  arrangement 
corresponds  with  the  order  in  which  they  emerge  as  cells 
at  a  later  period."  Surely,  however,  for  Weismann  of  all 
naturalists  it  ought  not  to  be  diiricult  to  find  tiiis  "  unknown 
controlling  force."  For  of  all  naturalists  he  is  perhaps  the 
most  ready  to  invoke  the  agency  of  natural  selection  as 
sufficient  to  explain  every  case — actual  or  imaginable — of 
adaptation.  Now,  here  is  a  case  where  natural  selection, 
one  would  think,  is  positively  bound  to  act — supposing 
that  there  be  such  things  as  gemmules.  For.  if  "  the 
carriers  of  heredity"  are  gemmules,  it  is  evident  that  their 
n^utual  "  affinities "  must  be  adaptivcly  "  marshalletl "  at 
each  step  of  phylogenetic  evolution,  before  any  further 
advance  of  such  evolution  can  be  possible.  And  1  do 
not  see  anything  more  "inconceivable"  in  sup|  osing  the 
establishment  of  such  mutual  affinities  step  l)y  stej)  tiirougli 
natural  selection,  than  in  supposing  any  other  course  of 
adaptive  develoi)ment  by  similar  means.  For,  as  Darwin 
has  well  shown,  while  anticipating  this  particular  objection 
to  his  theory, — "  The  assumed  elective  affinity  of  each 
gemmule  for  that  particular  cell  which  precedes  it  in  due 
order  of  development  is  supported  by  many  analogies." 
The  analogies  which  he  then  gives  are  so  numerous  that 
I  must  here  refer  to  his  own  discussion  of  the  sul)ject' — 
a  discussion  which  is  entirely  ignored  by  Weismann. 

Lastly,  the  principal  ground,  as  far  as  1  can  see, 
which  Weismann  has  for  regarding  Darwin's  theory  in 
any  shape  ''  inconceivable,"  is  his  own  supi)Osiiion  that 
there  is  as  complete  an  ainitomical  separation  between  the 


ik| 


Variation,  ike,  ind  ed.,  vol.  ii.  pp.  374-6. 
N 


iyS     An  Jixivnination  of  Wcisiuannism. 

som.i  and  its  ^erni-cells  as  there  is,  for  example,  between 
the  inumnKilian  soma  and  these  same  cells  when  afterwards 
detaclicd  from  the  ovary  and  developing  as  foetuses  in 
utero.  In  other  words,  the  only  connexion  is  supposed 
to  i)e  that  of  ieriving  nourishment  by  way  of  imbibition. 
Hut,  as  regards  the  germ-cell  while  still  forming  in  the 
ovary  or  testicle,  there  is  for  this  supi)Osition  no  basis  in 
fact.  There  is  nothing  in  the  histology  of  spermatogenesis 
that  lends  countenance  to  the  su{)position,  while  in  the  case 
of  the  ovum  such  histological  evidence  as  wc  posse^^s  makes 
altogether  against  it.     As  Professor  Vines  has  remarked : — 

It  cannot  be  seriously  maintained  that  the  whole  body  of  the 
embryo  is  developed  solely  from  the  germ-plasm  of  the  ovum. 
On  the  contniry,  since  the  embryo  is  developed  from  the  whole 
of  the  nucleus  and  more  or  less  of  the  cytoplasm  of  the  ovum, 
it  must  be  jdniittcd  that  the  non-gcrm-plasm  of  the  ovum 
provides  a  large  part  of  the  material  in  embryogcny.  It  is  an 
obvious  inference  that,  under  these  circumstances,  hereditary 
characters  may  be  transmitted  from  the  parent  to  the  offspring, 
not  only  by  the  germ-plasm,  but  also  by  the  somato-plasm,  of  the 
ovum  '. 

Again,  and  apart  from  this  consideration,  it  is  now 
known  that  a  very  intimate  network  of  protoplasmic  fibres 
connects  the  cell-contents  of  cellular  tissues,  both  in  plants 
and  animals.  So  that  here  we  have  another  very  possible 
means  of  communication  between  the  gcrm-cclls  and  the 
somatic-cells  which  together  constitute  a  multicellular 
organism. 

Therefore,  in  so  far  as  histology  can  be  trusted  to 
constitute  a  basis  for  generalizations  of  this  kind  at  all,  it 
does  not  sustain  the  supposition  that  there  can  be  no 
medium   of    communication   between   the   general  cellular 

'  Nature,  vol.  xl.  p.  624.  Wc|.smann's  answer  to  this  and  other  parts 
of  Professor  Vines'  criticism  where  the  term  "somatoplasm"  occurs,  will 
be  considered  later  on. 


Appendix  I. 


179 


lissues  of  ail  ori^.inism  and  ils  spct  iully  rc|iiodib  live 
clcuK-iits.  On  the  contrary,  the  microscope  is  able  to 
demonstrate  possible  roails  of  connexion — and  this  even 
upon  Weismann's  own  view  as  to  a  specialized  germinal 
substance  which  is  restricted  to  the  nucleus  of  an  ovum. 
In  short,  the  supposition  as  to  an  absolute  anatomical 
separation  between  germ-plasm  and  somato-j  'asm  is  a  de- 
duction from  Weismann's  theory  itself:  it  is  not  supported 
— it  is  discredited — by  histological  observation.  Hence, 
it  cannot  be  accepted  as  valid  evidence  in  favour  of  the 
theory  from  which  alone  it  is  derived,  or  as  a  valid 
objection  to  the  rival  theory  of  pangenesis. 

Once  more,  even  if  it  were  true  that  histology  proves 
an  absolute  anatomical  isolation  on  the  part  of  germ-cells, 
it  would  still  have  remained  unquestionable  that  there  is  no 
absolute  physiological  isolation.  For,  at  least,  the  germ- 
plasm  derives  ils  nourishment  from  the  soma  in  which  ii 
resides ;  and  who  shall  say  that  the  process  of  mere  imbibi- 
tion is  not  amply  sufficient  to  admit  of  the  passage  of 
"gemmules"?  Call  them  what  we  choose,  the  "carriers 
of  heredity  "  must  be  so  unimaginably  small,  that  in  relation 
to  histological  cells  they  must  be  as  gnats  to  camels.  Yet 
we  know  that  even  camels  in  the  form  of  "migrating  cells" 
of  various  kinds  are  able  to  pass  through  living  membranes ; 
and  we  also  know  that  the  microbes  of  syphilis  can 
penetrate  both  ova  and  spermatozoa.  Why  then  should  it 
be  deemed  inconceivable  that,  where  all  such  things  can 
pass,  gemmules  can  do  so  likewise? 

Lastly,  I  have  recently  spoken  of  the  detached  condition 
of  a  ripe  ovum  in  utero.  Now  it  seems  to  me  more  "  in- 
conceivable "  that  such  an  ovum  should  be  capable  of 
announcing,  as  it  were,  to  the  walls  of  the  uterus  v/helher  or 
not  it  is  in  a  fertilized  condition,  than  it  is  thf"/,  before  quit- 
ling  the  ovary,  it  should  have  had  some  kind  of  physiological 
converse  with  its  environing  soma.     Yet  it  is  certain  that, 

N   2 


f^'l 


I 


i8o    An  Examination  of  IVcismannism. 

Nvilhoiit  any  visible  mcilium  of  communication,  the  impreg- 
nated ovum  is  able  to  inform  the  uterus  that  it  is  impreg- 
nated; and  thereupon  the  uterus  behaves  towards  that 
ovum  in  an  altogether  astonishing  manner,  such  as  it  never 
•  lisplays  towards  an  unimpregnated  ovum.  Of  course  various 
hypotheses  may  now  be  formed  to  account  for  this  fact, 
seeing  that  no  one  can  question  it  as  a  fact.  But  sup- 
posing that  the  fact  could  be  questioned,  with  how  much 
greater  effect  might  it  be  argued  that  any  communication 
between  the  ovum  and  its  soma  is  even  more  antecedently 
incredible  when  the  ovum  is  entirely  free  than  when  it  is 
still  contained  within  its  ovary. 

Now  these,  as  far  as  1  can  find,  are  the  only  grounds 
for  VVeismann's  repeated  assertion  that  the  theory  of  pan- 
genesis in  any  form  is  "  inconceivable."  I  have  therefore 
endeavoured  to  show  that  this  is  too  strong  a  statement. 
.\11  the  facts  and  considerations  whereby  he  seeks  to  support 
it  were  present  to  the  mind  of  Darwin ;  and,  quite  apart  from 
any  quesli(jn  of  relative  authority,  I  cannot  avoid  agreeing 
with  Darwin  that,  whether  or  not  the  theory  is  true,  at  all 
events  the  "  difljcullies"  attaching  to  it  on  these  merely 
a  priori  grounds  are  not  insuperable,  or  such  as  to  render 
his  "pet  child"  an  unconceived  monstrosity  in  logic,  or 
a  proved  absurdity  in  science. 

Be  it  understood,  howevei,  that  I  am  not  here  defending 
the  theory  of  pangenesis.  I  am  investigating  the  theory 
of  germ-plasm ;  and  it  is  because  VVeismann  seeks  to 
sustain  the  latter  by  excluding  the  former  as  preposterous, 
that  I  have  been  obliged  thus  to  consider  the  validity  of 
his  criticism.  For  the  point  to  which  I  am  leading  is, 
that  Weismann  gains  nothing  in  the  way  of  support  to 
his  own  theory  by  this  disparagement  of  Darwin's,  unless 
he  can  show  thai  the  former  supplies  some  more  "  conceivable  " 
explanation  touching  the  mechanism  of  heredity.  Now  1  am 
unable  to  see  that  he    has  shown   this.     What  I  do  see 


Appendix  /. 


i8i 


is  that  his  a  priori  argument  from  "inconceivability" 
cuts  both  ways,  and  that  it  niakt-s  at  least  as  much  against 
germ-plasm  as  it  does  against  gcmmulcs.  Therefore, 
having  now  considered  what  Wcismann  has  said  against 
the  conceivability  of  gemmules  on  grounds  of  general 
reasoning,  I  shall  proceed  to  show  that  (juite  as  much — 
or  even  more — may  l)c  said  in  the  way  of  a  lu  qiioque. 
In  other  words,  we  have  now  fniished  with  the  second  of 
the  three  propositions  which  we  are  examining  (see  p.  71), 
and  proceed  to  our  consideration  of  the  third. 

First  of  all,  I  do  not  see  any  greater  difluulty  in 
supposing  that  the  " carriers  of  heredity"  proceed  cenlri- 
petally  from  somatic-cells  to  germ-cells,  than  in  supposing  that 
they  proceed  centrifiii;ally  .  am  the  germ-cells  to  the  somatic- 
cells  which  they  are  engaged  in  constructing.  Nor  do  I 
see  any  more  diflicull)i  in  imagining  these  "  carriers  of 
heredity"  to  be  capable  of  constructing  a  new  organism 
if  they  have  first  proceeded  centripetally,  and  are  thus 
severally  representative  of  all  parts  of  the  parent  organism 
after  its  construction  Juis  Imn  cciuplttcd,  than  I  do  if  they 
have  proceeded  centrilugiiiy,  and  are  thus  similarly  repre- 
sentative of  all  parts  of  that  organism  he/ore  its  construction 
has  been  commenced^. 

'  Wcismann  speaks  disparaginpjly  of  Darwin's  throry  as  a  "theory 
of  fyeformation  "  (p.  31(1).  "  \Vc  must  assume,"  )ie  adds  hy  way  of 
explanation,  "that  eacli  single  ])art  of  the  body  at  each  developmental 
stage  is,  from  tlie  first,  represented  in  the  j;erni-cell  as  distinct  particles 
of  matter,  whicli  will  reproduce  each  part  of  the  body  at  its  appropriate 
stage  as  their  turn  for  development  arrives,"  lliil  must  we  not  likewise 
"assume"  exactly  the  same  tliinj,'  in  the  case  of  Weismann's  own 
theory?  To  me,  at  any  rate,  it  apj'cars  tliat  the  desciiption  is  quite  as 
api)ropriate  to  germ-jda^m  as  it  i*  to  gemmules.  Nor  can  I  see  any 
distinction,  even  where  he  seeks  to  draw  it  more  expressly,  as  for 
instance — "Every  detail  in  the  wliole  ori;anism  must  be  represented  in 
the  germ-idasrn  by  its  own  special  and  peculiar  arrani,'ement  of  the 
groups  of  molecules, . .  .  not  imlei.  d  as  tlie  preformed  germsof  structure  (the 
gemmules  of  panj^enesis),  i)ut  as  variations  in  its  molecular  constitution." 
\_Essays,  p.  194.]     Again,  on  page  325  he  gives  a  foot-note  explaining 


■  .| 


1 82     An  Examination  of  IVeisnuinnism, 

Similarly,  it  seems  to  me,  whatever  cop;cncy  there  may  be 
in  Weismann's  objcdion  to  Darwin's  theory  on  the  score 
that  it  must  assume  "  an  unknown  controlling  force  in  order 
to  marshal  the  molecules,"  is  ecjually  great  as  regards  his 
own.  True,  Weismann  has  a  lot  to  say  about  the  control 
which  nuclco-plasm  can  exercise  on  cell-formal  ion,  and 
germ-plasm  on  marshalling  successive  stages  of  ontogeny ; 
hut  all  that  this  amounts  to  is  a  rc-statcment  of  the  facts. 
Such  a  controlling  force  must  he  i-qually  assumed  by  both 
theories;  but  in  each  alike  there  is  an  ab  ence  of  any  ghost 
of  an  explanation. 

Again,  whatever  difficulty  there  may  be  in  conceiving 
the  transition  of  somatic  substance,  mulalis  ?nii/<int//s  there 
must  be  an  equal  difficulty  in  conceiving  the  transition  of 
germinal  substance  into  somatic  substance.  Indeed,  as  far 
as  I  can  sec,  the  difficulty  is  even  greater  in  the  latter  case 
than  it  is  in  the  former.  For  the  very  essence  of  Weismann's 
view  is  that  germ-jjlasm  diders  from  all  or  any  other 
"plasm"  in  origin  or  kind:  germ-plasm,  and  germ-plasm 
alone,  has  been  immortal,  perpetually  continuous,  capable 
of  indefinite  self-mulliplication,  and  so  of  difTerentiating 
itself  into  an  endless  number  and  variety  of  somatic  tissues. 
But,  according  to  Darwin's  view,  there  is  not,  and  never 
has  been,  any  such  fundamental  difTerence  between  the 
essential  nature  of  somatic  elements,  and  the  essential 
nature  of  sexual  elements.  On  the  contrary,  it  is  supposed 
that  both  formative  and  formed  material  are  one  in  kind 


the  distinction  by  alluding;  to  the  controversy  between  the  preformation- 
ists  ami  cpij^eiiesists,  I!ut  the  theory  of  pant^Liiosis  does  not  supi)oscthe 
future  oiganism  to  exist  in  tlie  egg-cdl  as  a  viiuiaturc:  it  supposes 
merely  that  every  part  of  the  future  organism  is  represented  in  the  egg- 
ccll  by  corresponding  material  particles.  And  this,  as  far  as  I  can 
understand,  is  exactly  what  the  theory  of  germ-jdasm  supposes ;  only 
it  calls  the  particles  "molecules,"  and  seemingly  attaches  more  im- 
portance to  themattcr  of  variations  in  their  arrangement  or  "constitution," 
whatever  these  vague  expressions  may  be  intended  to  signify. 


Appendix  /, 


183 


lind 


— that  all  the  ccllul.ir  li-Mics  of  a  multicoUnlar  organism, 
like  the  sin<j;Ie  cell  of  a  unicclliilir  or<j;;uiism,  are  per  st 
endowed  wiih  the  vital  proi)erty  of  self-muliij^lication ;  and 
that  whether  this  proptMty  finds  its  expivssion  in  normal 
growth,  in  abnormd  increments  of  j^rowth  (such  as  tumours), 
in  processes  of  repair,  in  the  various  forms  of  a-sexual 
reproduct  on,  or  in  the  more  specialized  form  of  sexual 
fertilization,  there  is  everywhere  an  exhibition  of  one  and 
the  same  capacity.  Now,  without  f^oing  further  tiian  this 
contrast  between  the  fundamental  principles  of  the  two 
theories,  does  it  not  become  evident  that  the  difficulty  of 
conceivinj;  a  transition  of  A  into  A'  is  at  any  rale  no 
greater  than  that  of  conceiving  a  transition  of  A  into  B, 
where  A  is  in  both  cases  the  formau.c  substance,  A'  this 
same  substance  in  another  sta-  of  evolution  (i.e.,  elaboratid 
for  the  performance  of  some  special  function,  but  never 
so  as  to  lose  its  original  function  A),  while  li  is  a  substance 
which  differs  from  A  almost  as  much  as  a  woven  texture 
differs  from  the  hands  that  weave  it? 

Once  more,  in  all  his  arguments  which  are  directed  to 
prove  the  continuity  of  germ-plasm,  VVeismann  nowhere 
seems  to  perceive  the  necessity  of  arguing  the  correlative 
hypothesis — viz.,  that  of  the  discontinuity  of  som.Uo-plasm. 
Yet,  as  Professor  Vines  has  remarked,  it  is  as  incuml)ent 
on  him  to  disprove  any  possible  continuity  on  the  part  of 
somato-plasm,  as  it  is  to  prove  a  perpetual  continuity  on 
the  part  of  germ-plasm.  And  here  I  am  disposed  to  go 
further  than  Professor  Vines  has  gone;  for  it  apjtears  to  me 
even  more  incumbent  on  Weismann  to  argue  a  discontinuity 
on  the  part  of  somato-plasm,  than  it  is  on  him  to  argue 
a  continuity  on  the  part  of  germ-plasm. 

This  must  be  immediately  apparent  if  we  remember  that, 
unless  the  discontinuity  of  somato-plasm  be  assumed,  the 
theory  of  the  continuity  of  germ-plasm  in  telluric  time  (as 
distinguished  from  eternity)  becomes  identical  in  form  with 


Ml 


III 


I? 


184    An  Examination  of  U^isiuamiisni. 


all  those  theories  of  heredity  to  the  Ainiily  of  which  pan- 
genesis belongs.  All  these  theories  go  upon  the  assumption 
that  living  material  has  been  continuous  in  telluric  time — 
i.e.,  always  derived  from  pre-existing  material  of  the  same 
kind  ;  but  they  embody  the  further  assumption  that  all  living 
material  is  material  of  the  same  kind  —  i.e.,  everywhere 
presents  the  same  fundamental  properties.  Weismann's 
theory  on  the  other  hand,  while  adopting  the  first  assump- 
tion, rejects  ihe  second ;  and  assumes  in  its  stead  that  living 
material  exists  in  "  two  kinds,"  only  one  of  which  has  been 
continuous,  while  the  other  is  discontinuous — being,  in  fact, 
formed  anew  at  each  ontogeny.  Therefore,  to  my  mind,  it 
seems  more  needful  to  aigue  the  point  wherein  his  theory 
dilTers  from  these  other  theories  of  heredity,  than  it  is  to 
argue  the  point  wherein  it  agrees  with  them.  We  look  to 
him  for  a  proof  of  the  discontinuity  of  somato-plasin  much 
more  than  we  do  for  a  proof  of  the  continuity  of  germ-plasm. 
Now  the  only  proof  that  he  has  to  give  of  the  discontinuity 
of  somato-plasm— or,  in  other  words,  that  the  self-multiplica- 
tion of  somatic  cells  cannot  take  i)lace  unless  the  nucleus  of 
each  contains  a  self-multiplying  idio-plasm  derived  from  the 
nucleus  of  a  germ-cell — is  the  non-transmissibility  of  somato- 
gcnetic  characters.  Here,  however,  there  is  an  obvious 
equivoque.  For  his  only  test  of  characters  as  somatogenetic 
and  blastogenetic  consists  in  observing  whether  or  not  they 
are  inherited :  if  they  are  inherited,  he  says  they  are  blasto- 
genetic :  if  they  are  not  inherited,  he  says  they  are  somato- 
genetic. But  this  is  manifestly  circular  reasoning,  so  long 
as  the  question  in  debate  is  as  to  the  truth  of  his  theory. 
What  we  require  in  proof  of  the  distinguishing  feature  of  that 
theory -i.e.,  the  discontinuity  of  the  hypothetical  somato- 
plasm— is  not  merely  the  obvious  fact  that  some  characters 
are  inherited  while  others  are  not,  but  independent  proof 
that  inherited  and  non-inherited  characters  correspond  to 
a  continuity  of  germ-plasm  on  the  one  hand,  and  a  dis- 


Appefidjx  I, 


185 


conlimiity  of  somato-plasm  on  llie  otlier.  He  shows  us, 
indeed,  what  was  well  known  before,  that  characters  developed 
during  the  lifetime  of  the  individual  are  seldom  (if  ever) 
inherited,  while  characters  developed  during  the  lifetime  of 
the  species  are  always  inherited.  Obviously,  however,  this 
fact  is  no  proof  of  the  assumed  correlation  just  mentioned, 
because,  as  Darwin  has  clearly  pointed  out,  it  may  very  well 
be  due  to  the  much  shorter  time  which  has  been  allowed  for 
what  may  be  termed  the  impress  of  heredity.  Therefore, 
supposing  (with  Darwin  and  others)  that  living  material  is  all 
of  one  kind,  and  continuous,  the  fact  on  which  Weismann 
relies  admits  of  being  explained  without  resorting  to  his  more 
complex  supposition  of  living  material  in  two  kinds,  the  one 
perpetually  continuous,  and  the  other  interrupted  at  each 
ontogeny. 

For  these  reasons  it  appears  to  me  that,  so  far  as  the 
argument  from  "inconceivability"  is  concerned,  it  makes  at 
least  as  much  against  the  theory  of  qerm-plasm  as  it  does 
against  the  theory  of  pangenesis ;  and,  therefore,  that  no 
argumentative  advantage  is  gained  from  its  use  by  Weismann. 
The  truth  probably  is  that,  whaiivcr  the  mechanism  of 
heredity  may  actually  be,  it  is  at  once  so  minute  and 
so  complex  that  its  action  is  '•  inconceivable,"  or,  more 
correctly,  unimaginable.  Be  it  again  understood,  therefore, 
that  I  am  not  arguing  in  favour  of  i)angenesis.  I  am  merely 
criticising  what  apjiears  to  me  an  unsound  argument  in 
favour  of  germ-plasm.  All  this  general  or  merely  a  priori 
reasoning  with  regard  to  inconceivability  is,  as  I  have 
attempted  to  show,  as  available  on  the  one  side  as  on  the  other, 
and  so  fails  to  yield  any  observable  advantage  to  either. 


In  conclusion  it  must  be  noticed,  that  Weismann  now 
appears  to  have  himself  perceived  the  grave  ditliculties  whit  h 
lie  against  his  aniithesis  between  a  hypothetical  "germ- 
plasm  "  and  a  hypothetical  "somato-plasm,"  notwithstanding 


1 86    An  Examination  of  Weismannism. 

that  the  former  becomes  converted  into  the  latter  at  each 
ontogeny.  At  any  rate,  he  allows  that  Vines'  criticism  upon 
this  head  is  sound.  But  he  is  strongly  of  the  opinion  that, 
by  means  of  a  later  emendation  of  his  theory  as  originally 
published,  he  has  succeeded  in  obviating  these  difficulties 
in  toio.  For  my  own  part,  as  already  several  times  observed 
in  the  text,  I  cannot  in  the  least  perceive  that  such  is  the 
case ;  and  theicfore  I  will  quote  in  exiemo  what  he  has  said 
in  answer  to  Professor  Vines.  It  will  be  seen  that  his  newer 
emendation  of  the  theory  consists  in  substituting  for  his 
original  "  somato-plasm "  two  substances,  which  are  called 
respectively  "  somatic  idio-plasm ''  and  "  cytoplasm.**  And 
it  is  by  means  of  this  substitution  that  he  thinks  he  has,  in 
some  way  or  another,  overcome  the  contradiction  involved  in 
the  doctrine  (and,  as  it  still  seems  to  me,  the  essential 
doctrine  of  his  whole  theory  of  heredity)  that  "  germ-plasm  ** 
becomes  converted  into  "  somato-plasm  "  during  the  course 
of  every  ontogeny.  The  following,  at  any  rate,  is  his  latest 
utterance  upon  the  subject : — 


I  believe  that  the  objections  which  Professor  Vines  makes  to 
my  theory  of  the  continuity  of  germ-plasma  rest  solely  on  an 
unintentional  confusion  of  my  ideas,  as  he  compares  the  opinions 
expressed  in  the  second  essay  with  those  of  the  later  ones, 
with  which  they  do  not  tally.  I  will  endeavour  to  make  this 
clear.  In  this  second  essay  (1883)  I  contrasted  the  body  (soma) 
with  the  germ-cells,  and  explained  heredity  by  the  hypothesis 
of  a  "  Vererbungs-substanz  "  in  the  germ-cells  (in  fact  the  germ- 
plasma),  which  is  transmitted  without  breach  of  continuity  from 
one  generation  to  the  next.  I  was  not  then  aware  that  this  lay 
only  in  the  nucleus  of  the  ovum,  and  could  therefore  contrast 
the  entire  substance  of  the  ovum  with  the  substance  of  the 
body-cells,  and  term  the  latter  "somato-plasm."  In  Essay  IV 
(1885)  1  had  arrived,  like  Strasburger  and  O.  Hertwig,  at  the 
conviction  that  the  nuclear  substance,  the  chromatin  of  the 
nuclear  loops,  was  the  carrier  of  heredity,  and  that  the  body  of 
the  cell  was  nutritive  but  not  formative.     Like  the  investigators 


Appendix  I. 


187 


just  named,  I  transferred  the  conception  of  idio-plasm,  which 
Nageli  had  enunciated  in  essentially  dififcrcnt  terms,  to  the 
"  Vererbungs-substanz "  of  the  ovum-nucleus,  and  laid  down 
that  the  nuclear  chromatin  was  the  idio-plasm  not  only  of  the 
ovum  but  of  every  cell,  that  it  was  the  dominant  cell-element 
which  impressed  its  specific  character  upon  the  originally 
indifferent  cell-mass.  From  then  onwards,  I  no  longer  desig- 
nated the  cells  of  the  body  simply  as  "  somato-plasm,"  but 
distinguished,  on  the  one  hand,  the  idio-plasm  or  "  Anlagcn- 
plasma"  of  the  nucleus  from  the  cell-body  or  "  Cytoplasma,'* 
and,  on  the  other,  the  idio-plasm  of  the  ovum-nucleus  from  that 
of  the  somatic  cell-nucleus  ;  I  also  for  the  future  applied  "  germ- 
plasm  "  to  the  nuclear  idio-plasm  of  ovum  and  spermatozoon, 
and  "somatic  idio-plasm"  to  that  of  the  body  cells  (e.g,  p.  it'4). 
The  embryogenesis  rests,  according  to  my  idea,  on  alterations 
in  the  nuclear  idio-plasm  of  the  ovum,  or  "germ-plasm";  on 
p.  1S6,  et  seq.,  is  pictured  the  way  in  which  the  nuclear  idio- 
plasm is  halved  in  the  first  ccll-divicion,  undergoing  regular 
alterations  of  its  substance  in  such  a  way  that  neither  half 
contains  all  the  hereditary  tendencies,  but  the  one  daughter- 
nucleus  has  those  of  the  ectoblast,  the  other  those  of  the  cnto- 
blast ;  the  whole  remaining  embryogenesis  rests  on  a  con- 
tinuation of  this  process  of  regular  alterations  of  the  idio-plasm. 
Each  fresh  cell-division  sorts  out  tendencies  which  were  mixed 
in  the  nucleus  of  the  mother-cell,  until  the  complete  mass  of 
embryonic  cells  is  formed,  each  with  a  nuclear  idio-plasm  which 
stamps  its  specific  histological  character  on  the  cell. 

I  really  do  not  understand  how  Professor  Vines  can  find  such 
remarkable  difficulties  in  this  idea.  The  appearance  of  the 
sexual  cells  generally  occurs  late  in  the  embryogcny  ;  in  order, 
then,  to  preserve  the  continuity  of  germ-i)l,ism  from  one 
generation  to  the  next,  I  propound  the  hypothesis  that  in 
segmentation  it  is  not  all  the  germ-plasm  (i.e.  idio-plasm  of  the 
first  ontogenetic  grade)  which  is  transformed  into  the  second 
grade,  but  that  a  minute  portion  remains  unaltered  in  one  of 
the  daughter-cells,  mingled  with  its  nuclear  idio-plasm,  but  in 
an  inactive  state  ;  and  that  it  traverses  in  this  manner  a  longer 
or  shorter  series  of  cells,  till,  reaching  those  cells  on  which  it 
stamps  the  character  of  germinal  cells,  it  at  last  assumes  the 


1 88    An  Examination  of  Weismanmsm. 

active  state.  This  hypothesis  is  not  purely  gratuitous,  but  is 
supported  by  observations,  notably  by  the  remarkable  wander- 
ings of  the  germinal  cells  of  Hydroids  from  their  original 
positions. 

But  let  us  neglect  the  proba'^ility  of  my  hypothesis,  and 
consider  nurcly  its  logical  accuracy.  I'rofcssor  Vines  says: — 
"  The  fate  of  the  germ-plasm  of  the  fertilized  ovum  is,  according 
to  Professor  Weismann,  to  be  converted  in  part  into  the  somato- 
plasm (!)  of  the  embryo,  and  in  part  to  be  stored  up  in  the 
germ-cells  of  the  cmbrj'o.  This  being  so,  how  are  we  to  conceive 
that  the  germ-plasm  of  the  ovum  can  impress  upon  the  somato- 
plasm (!)  of  the  developing  embryo  the  hereditary  character  of 
which  it  (the  germ-plasm)  is  the  bearer.''  This  function  cannot 
be  discharged  by  that  portion  of  th  germ-plasm  of  the  ovum 
which  has  become  converted  into  the  somato-plasm  (1)  of  the 
embryo,  for  the  simple  reason  that  it  has  ceased  to  be  germ-plasm^ 
and  must  therefore  have  lost  the  properties  characteristic  of  that 
substance.  Neither  can  it  be  discharged  by  that  portion  of  the 
germ-plasm  of  the  ovum  which  is  aggregated  in  the  germ-cells 
of  the  embryo,  for  under  these  circumstances  it  is  withdrawn 
from  all  dirert  relation  with  the  developing  somatic-cells.  The 
question  remains  without  an  answer."  I  believe  myself  to  have 
answered  this  above.  I  do  not  recognize  the  somato-plasm  of 
Professor  Vines  ;  my  germ-plasm,  or  idio-plasm  of  the  first 
ontogenetic  grade,  is  not  modified  into  the  somato-plasm  of 
Professor  Vines,  but  into  idio-plasm  of  the  second,  third,  fourth, 
hundredth,  &c.  grade,  and  every  one  impresses  its  character  on 
the  cell  containing  it. 


:1  ;i 


It  may  be  dullness,  but  I  confess  that  this  does  not 
appear  to  me  an  "  answer "  to  Professor  Vines'  criticism. 
Even  though  "  idio-plasm  of  the  first  ontogenetic  grade " 
has  to  become  "  idio-plasm  of  the  second,  third,  fourth, 
hundredth,  &c.  grade,"  before  in  each  of  the  grades  con- 
cerned it  can  give  origin  to  the  somatic-cells  which  are 
distinctive  of  that  grade,  I  cannot  see  that  it  makes  any 
difference  (in  relation  to  Vines'  criticism)  whether  we  speak 
of  those  cells   as  containing  "somato-plasm,"  or  as  con- 


Appendix  I, 


1S9 


taininp;  "somatic  idio-plasm "  of  such  and  such  a  grade, 
//wj '•  cytoplasm."  For  whether  we  thus  follow  Weismann's 
earlier  terminology  or  his  later,  we  are  so  far  speaking 
about  exactly  the  same  thing,  namely,  the  transformation  of 
"  germ-plasm  "  into  all  the  constituent  cells  of  the  "  soma." 
The  difficulty  is,  in  Vines'  words  above  cited,  "  to  con- 
ceive that  the  germ-plasm  of  the  ovum  can  impress  upon 
the  somato-plasm  of  the  developing  embryo  the  hereditary 
characters  of  which  it  (the  germ-plasm)  is  the  bearer " ; 
and  Weismann  says  that  this  difliculty,  which  he  acknow- 
ledges, can  now  be  answered  by  substituting  for  his 
original  statement  that  "germ-plasm"  becomes  changed 
into  "  somato-plasm,"  the  statement  that  it  is  "  idio-plusm  " 
derived  from  "  germ-plasm "  which  thus  "  impresses  its 
character  on  the  cell  containing  it."  But,  ''  as  a  matter 
of  logical  accuracy,"  there  is  surely  here  a  distinction 
without  a  difTerence.  For  what  is  the  difTerence  between 
saying  that  germ-plasm  "impresses"  its  character  on  the 
contents  of  all  somatic  cells  considered  collectively  under 
the  term  "somato-plasm,"  and  saying  that  every  "onto- 
genetic grade "  of  germ-plasm  "  impresses "  its  character 
on  each  successive  group  ot  somadc  cells  considered  sever- 
ally under  the  term  "  idio-plasm "  oi  such  and  such  a 
grade?  At  best  this  newer  terminology  has  reference 
merely  to  a  superadded  hypothesis  touching  the  mode — 
or  rather  the  history — of  the  nsition  in  question :  it 
does  not  affect  the  original  and  essential  doctrine  of  the 
transition  itself. 


APPENDIX    II: 

ON    TELEGONY. 

A  WIDELY  different  view,  however,  is  taken  by  Mr.  Herbert 
Spencer  with  regard  to  the  theoretical  interpretation  of  tele- 
gony.  This,  indeed,  is  precisely  the  opposite  view  to  the 
one  which  is  given  in  the  text.  For  while  I  agree  with 
Professor  Weismann  in  holding  that  the  facts  of  telcgony 
(supposing  them  to  be  facts)  are  as  compatible  with  the 
theory  of  germ-plasm  as  with  that  of  gemmulcs,  "  physio- 
logical units,"  or  any  other  theory  which  postulates  a  centri- 
petal flow  of  the  carriers  of  heredity  from  somatic-cells  to 
germ-cells,  Mr.  Spencer  is  of  the  opinion  that  these  facts  are 
destructive  of  any  theory  which  postulates  a  continuity  in  the 
substance  of  heredity — i.  e.,  a  centrifugal  flow  of  the  carriers 
of  heredity.  And,  imquestionably,  Mr.  Spencer's  view  is  the 
prevalent  one.  Therefore,  seeing  that  his  opinion  is  not 
only  of  weight />fr  se,  but  is  shared  by  the  scientific  world  in 
general,  I  will  here  transcribe  a  somewhat  lengthy  discussion 
which  I  have  recently  held  with  him  upon  the  subject. 

In  the  Contemporary  Review  for  March,  Mr.  Spencer  wrote 
as  follows:  — 


We  pass  now  to  evidence  not  much  known  in  the  world  at 
large,  but  widely  known  in  the  biological  world,  though  known 
in  so  incomplete  a  manner  as  to  be  undervalued  in  it.  Indeed, 
when  I  name  it  probably  many  will  vent  a  mcital  pooh-pooh. 
The  fact  to  which  I  refer  is  one  of  which  record  is  preserved 


It 


192    An  Exaviination  of  IVeisniannism. 

in  the  museum  of  the  College  of  Surgeons,  in  the  shape  oi 
paintings  of  a  foal  borne  by  a  mare  not  quite  thoroughbred, 
to  a  sire  wliich  was  thoroughbred— a  foal  which  bears  the 
markings  of  the  quagga.  The  history  of  this  remarkable  foal 
is  given  by  the  Karl  of  Morton,  F.K.S.,  in  a  letter  to  the  Presi- 
dent of  the  Royal  Society  (read  November  23,  1820).  In  it  he 
states  that  wishing  to  domesticate  the  quagga,  and  having 
obtained  a  male,  but  not  a  female,  he  made  an  experiment. 

I  tried  to  breed  from  the  male  quag[,'a  and  a  youn^j  chotnut  mare  of 
seven-eighths  Aratiian  Moud,  and  whicl)  had  never  been  bred  from ;  the 
result  was  the  production  of  a  female  hybrid,  now  Ove  years  old,  and 
bearing,  both  in  her  form  and  in  her  colour,  very  decided  indications  of 
her  mixed  origin.  I  subseciuently  parted  with  tlie  seven-eighths  Arabian 
mare  to  Sir  Gore  Ouseley.  who  has  bred  from  her  by  a  very  fine  black 
Arabian  horse.  I  yesterday  morning  examined  the  produce,  namely, 
a  two-year-old  filly  and  a  year-old  colt.  They  have  the  character  of  the 
Arabian  breed  as  decidedly  as  can  be  expected,  where  fifteen-sixttenths 
of  the  blood  are  Arabian;  and  they  arc  fine  specimens  of  that  breed; 
but  both  in  their  colour  and  in  the  hair  of  their  manes  they  have 
a  striking  resemblance  to  the  quagga.  Their  colour  is  bay,  marked 
more  or  less  like  the  quagga  in  a  darker  tint.  I5olh  are  distinguished 
by  the  dark  line  along  the  ridge  of  tiie  back,  the  dark  stripes  across  the 
fore-hand,  and  the  dark  bars  across  the  back  part  of  the  legs '. 

Lord  Morton  then  names  sundry  further  correspondences. 
Dr.  Wollaston,  at  that  time  President  of  the  Royal  Society, 
who  had  seen  the  animals,  testified  to  the  correctness  of  his 
description,  and,  as  shown  by  his  remarks,  entertained  no 
doubt  about  the  alleged  fact."^  But  good  reason  for  doubt 
may  be  assigned.  There  naturally  arises  the  question — How 
does  it  hajjpen  that  parallel  results  are  not  observed  in  other 
cases?  If  in  any  progeny  certain  traits  not  belonging  to  the 
sire,  but  belonging  to  a  sire  of  preceding  progeny,  are  re- 
produced, how  is  it  that  such  anomalously-inherited  traits  are 
not  observed  in  domestic  animals,  and  indeed  in  mankind  ? 
How  is  it  that  the  children  of  a  widow  by  a  second  husband  do 
not  bear  traceable  resemblances  of  the  first  husband  ?  To  these 
questions  nothing  like  satisfactory  replies  seem  forthcoming ; 

*  •  rnildsophical  Transactions  of  the  Royal  Society  for  the  Year  1831,' 
Part  I.  pp,  20-24. 


Appendix  II. 


193 


and,    in   the   absence   of  replies,   scepticism,  if   not    disbclitf, 
may  be  held  reasonable. 

There  is  an  explanation,  however.  Forty  years  ago  I  made 
acquaintance  with  a  fact  which  impressed  me  by  its  sij^nificant 
implications;  and  has,  for  this  reason  1  suppose,  remained  in  my 
memory.  It  is  set  forth  in  \\\Kt  Joiinuil  of  the  Royal  Ay^ricttl- 
iural  Society,  vol.  xiv.  (1X53),  pp.  214  et  seq.,  and  concerns 
certain  results  of  crossin<j  English  and  French  breeds  of  sheep. 
The  writer  of  the  translated  paper,  M.  Malingie-Nouel,  Director 
of  the  Agricultural  School  of  Fa  Cliarmoise,  slates  that  when 
the  French  breeds  of  sheep  (in  which  were  inckided  "the 
;//<7;/^;'^/ Merinos")  were  crossed  with  an  lOnglish  breed,  "the 
lambs  present  the  following  results.  Most  of  them  resemble  the 
mother  more  than  the  father  ;  some  show  no  trace  of  the  father."' 
Joining  the  admission  respecting  the  mongrels  with  the  facts 
subsequently  stated,  it  is  tolerably  clear  that  the  cases  in  which 
the  lambs  bore  no  traces  of  the  father  were  cases  in  which  the 
mother  was  of  pure  breed.  Speaking  of  the  results  of  these 
crossings  in  the  second  generation  "  having  seventy-five  per  cent, 
of  English  blood,"  M.  Nouel  says: — "The  lambs  thrive,  wear 
a  beautiful  appearance,  and  complete  the  joy  of  the  breeder.  .  .  . 
No  sooner  are  the  lambs  weaned  than  their  strength,  their 
vigour,  and  their  beauty  begin  to  decay.  ...  At  last  the  con- 
stitution gives  way  .  .  .  he  remains  stunted  for  life":  the 
constitution  being  thus  proved  unstable  or  unadaptcd  to  the 
requirements.  How,  then,  did  M.  Nouel  succeed  in  obtaining 
a  desirable  combination  of  a  fme  English  breed  with  the  rela- 
tively poor  French  breeds  ? 

He  took  ail  animal  from  "  flocks  originally  sprung  from  a  nii\iurc  of 
the  two  distinct  races  tliat  are  established  in  these  two  provinces 
[Herry  and  La  Sologne],"  and  these  he  "united  with  animals  of  another 
mixed  breed  .  .  .  whicii  blended  tiie  Touiangelle  and  native  Merino 
blood  of"  La  IJeauce  and  Touraine,  and  obtained  a  mixture  of  all  four 
races" without  decided  character,  without  fixity,  .  .  .  but  possessing  the 
advantage  of  being  used  to  our  climate  and  management." 

Putting  one  of  these  "mixed-blood  ewes  to  a  pure  New- Kent  ram 
.  .  .  one  obtains  a  lamb  containing  fifty-hundred ths  of  the  purest  and 
most  ancient  English  blood,  with  twelve  and  a-half  hundredths  of  four 
:lifferent  French  races,  which  are  individually  lost  in  the  preponderance 
af  English  blood,  and  disappear  almost  entirely,  leaving  the  improving 


k^" 


r94    ^n  Examinatioti  of  Wcisffiamii'sm. 

tyjie  in  the  ascendant.  .  .  .  All  tlic  lainhs  produced  strikingly  resembled 
vach  other,  and  even  Englishmen  took  tliem  for  animals  of  their  own 
country." 

M.  Noucl  jjoes  on  to  remark  that  when  this  derived  breed  was 
bred  with  itself,  the  marks  of  the  Krei>ch  breeds  were  lost. 
"  Some  sli^'ht  traces  could  be  detected  by  experts,  but  these 
soon  disappeared." 

Thus  we  get  proof  that  relatively  pure  constitutions  pre- 
dominate in  proj^eny  over  much  mixed  constitutions.  The 
leason  is  not  difficult  to  see.  Every  organism  tends  to  become 
adapted  to  its  conditions  of  life ;  and  all  the  structures  of 
a  species,  accustomed  through  multitudinous  generations  to  the 
climate,  food,  and  various  influences  of  its  locality,  are  moulded 
into  harmonious  co-operation  favourable  to  life  in  that  locality  : 
the  result  being  that  in  the  development  of  each  young  indi- 
vidual, the  tendencies  conspire  to  produce  the  fit  organization. 
It  is  otherwise  when  the  species  is  removed  to  a  habitat  of 
different  character,  or  when  it  is  of  mixed  breed.  In  the  one 
case  its  organs,  partially  out  of  harmony  with  the  requirements 
of  its  new  life,  become  partially  out  of  harmony  with  one  another ; 
since,  while  one  influence,  say  of  climate,  is  but  little  changed, 
another  influence,  say  of  food,  is  much  changed  ;  and,  con- 
secjuently,  the  perturbed  relations  of  the  organs  interfere  with 
their  original  stable  equilibrium.  Still  more  in  the  other  case  is 
there  a  disturbance  of  equilibrium.  In  a  mongrel  the  constitu- 
tion derived  from  each  source  repeats  itself  as  far  as  possible. 
Hence  a  conflict  of  tendencies  to  evolve  two  structures  more  or 
less  unlike.  The  tendencies  do  not  harmoniously  conspire ; 
but  produce  partially  incongruous  sets  of  organs.  And  evidently 
where  the  breed  is  one  in  which  there  are  united  the  traits  of 
various  lines  of  ancestry,  there  results  an  organization  so  full  of 
small  incongruities  of  structure  and  action,  that  it  has  a  much- 
diminished  power  of  maintaining  its  balance  ;  and  while  it 
cannot  withstand  so  well  adverse  influences,  it  cannot  so  well 
hold  its  own  in  the  offspring.  Concerning  parents  of  pure  and 
mixed  breeds  respectively,  severally  tending  to  reproduce  their 
own  structures  in  progeny,  we  may  therefore  say,  figuratively, 
that  the  house  divided  against  itself  cannot  withstand  the  house 
of  which  the  members  are  in  concord. 


1 


! 


Appendix  II. 


195 


Now  if  this  is  shown  to  be  the  case  with  breeds  the  purest  of 
which  have  been  adapted  to  their  habitats  and  nioilcs  of  life 
durinjj  some  few  hundred  years  only,  what  shall  we  say  when  the 
question  is  of  a  breed  which  has  had  a  constant  mode  of  life  in 
the  same  locality  for  ten  thousand  years  or  more,  like  the  (pia^Ha  ? 
In  this  the  stability  of  constitution  must  be  such  as  no  domestic 
animal  can  approach.  Relatively  stable  as  may  have  been  the 
constitutions  of  Lord  Morton's  horses,  as  compared  with  the 
constitutions  of  ordinary  horses,  yet,  since  Arab  horses,  even  in 
their  native  country,  have  probably  in  the  course  of  successive 
conquests  and  migrations  of  tribes  become  more  or  less  mixed, 
and  since  they  have  been  subject  to  the  conditions  of  domestic 
life,  differing  much  from  the  conditions  of  their  original  wild  life, 
and  since  the  English  breed  has  undergone  the  perturbing 
effects  of  change  from  the  climate  and  food  of  the  East  to  the 
climate  and  food  of  the  West,  the  organizations  of  the  horse  and 
mare  in  question  could  have  had  nothing  like  that  perfect  balance 
produced  in  the  quagga  by  a  hundred  centuries  of  harmonious 
co-operation.  Hence  the  result.  And  hence  at  the  same  time 
the  interpretation  of  the  fact  that  analogous  phenomena  are  not 
perceived  among  domestic  animals,  or  among  ourselves  ;  since 
both  have  relatively  mixed,  and  generally  extremely  mixed,  con- 
stitutions, which,  as  we  see  in  ourselves,  have  been  made 
generation  after  generation,  not  by  the  formation  of  a  mean 
between  two  parents,  but  by  the  jumbling  of  traits  of  the  one 
with  traits  of  the  other,  until  there  exist  no  such  conspiring 
tendencies  among  the  parts  as  cause  repetition  of  combined 
details  of  structure  in  posterity. 

Expectation  that  scepticism  might  be  felt  respecting  this 
alleged  anomaly  presented  by  the  quagga-marked  foal,  had  led 
me  to  think  over  the  matter  ;  and  I  had  reached  this  inter- 
pretation before  sending  to  the  College  of  Surgeons  Museum 
(being  unable  to  go  myself)  to  obtain  the  particulars  and  refer  to 
the  records.  When  there  was  brought  to  me  a  copy  of  the 
account  as  set  forth  in  the  "  Philosophical  Transactions,"  it  was 
joined  with  the  information  that  there  existed  an  appended 
account  of  pigs,  in  which  a  parallel  fact  had  been  observed. 
To  my  immediate  inquiry — "  Was  the  male  a  wild  pig.-"' — there 
came  the  reply  :  "  I  did  not  observe."     Of  course  I  forthwith 

O   2 


196    An  Iixiiniinaliou  of  ]l\isiiiiinnisin. 

obtained  the  vohiinc,  and  there  found  what  1  expected.  It 
was  contained  in  a  |)a|)(r  ( ommiinicited  by  Dr.  W'ollaston  from 
Daniel  (iiles,  I'lsc|.,  concerniiiy  liis  "  sow  anil  her  produce,"  which 
said  tiiat 

she  was  uiic  111  a  well-known  lilark  and  wliitc  hurd  ol  Mr.  NVeslcrn, 
the  Member  lor  l^s^ex.  Alxait  ten  ye.nrs  since  I  |>iil  hir  lo  a  f)o.nr  of  the 
wild  liriiMJ.  and  of  a  <leep  clustniit  eidoiir,  wliicli  1  had  jiisl  receisxil 
liom  llaltielij  House,  and  which  was  soon  aricrw.ods  drowned  by 
accident.  Thi-  pij;s  produced  (which  were  her  lirst  litter)  paitook  in 
nppearnncc  of  both  boar  and  sow.  but  in  some  the  che<<tnut  colour  of  the 
boar  stron^jly  iirevailed. 

The  sow  w.as  afterwards  put  to  a  boar  of  Mr.  Western's  breed  (the 
wild  boar  havin;;  been  lonj,'  dead).  The  produce  was  a  litter  of  jti^s 
some  of  which,  we  observed  with  much  ^urpiise,  to  be  stained  an<l 
clearly  marked  with  the  chestnut  cole  ur  which  had  prevailed  in  the 
I'lrnier  litter. 


IMr.  (iiles  adds  that  in  a  second  litter  of  [)i,L;s,  the  fatherof  which 
was  of  Mr.  Western's  breed,  he  and  his  bailiff  believe  there  was 
a  recurrence,  in  some,  of  the  chestnut  colour,  but  admits  that 
their  "recollection  is  much  less  peifect  than  1  wish  it  to  be." 
He  also  adds  that,  in  the  course  of  many  years'  experience,  he 
had  never  known  the  least  appearance  of  the  chestnut  colour  in 
Mr.  Western's  breed. 

What  are  tlie  probabilities  that  these  two  anomalous  results 
should  have  arisen,  under  these  exceptional  conditions,  as 
a  matter  of  chance?  Evidently  the  probabilities  against  such 
a  coincidence  are  enormous.  The  testimony  is  in  both  cases 
so  good  that,  even  apart  from  the  coincidence,  it  would  be 
unreasonable  to  reject  it ;  but  the  coincidence  makes  accept- 
ance of  it  imperative.  There  is  mutual  verification,  at  the 
same  time  that  there  is  a  joint  interpretation  yielded  of  the 
strange  phenomenon,  and  of  its  non-occurrence  under  ordinary 
circumstances. 

And  now,  in  the  presence  of  these  facts,  what  are  we  to  say? 
Simply  that  they  are  fatal  to  Weismann's  hypothesis.  They 
show  that  there  is  none  of  the  alleged  independence  of  the 
reproductive  cells  ;  but  that  the  two  sets  of  cells  arc  in  close 
communion.  They  prove  that  while  the  reproductive  cells 
multiply  and  arrange  themselves  during  the  evolution  of  the 


Appendix  11. 


197 


embryo,  some  of  their  ffcnn-plasin  |)ii!>sfs  into  the  mass  of 
soinatic-cclls  constituting'  the  parental  Ixuly,  and  becomes 
a  permanent  component  of  it.  Further,  tliey  necessitate  the 
inference  that  this  introduced  ^erm-plasm,  everywhere  ilifTused, 
is  some  of  it  inchided  in  the  reproductive  cells,  suhsetjuently 
formed.  .And  if  we  thus  jjet  a  dciiKinstration  that  tin;  some- 
what different  units  of  a  forei^^n  Ki''''""Pl''^'i^  permeating  the 
organism,  permeate  also  the  sul)sei|uently-lnrnied  reproductive 
cells,  and  affect  the  structures  of  the  individuals  arising  from 
them,  the  implication  is  that  the  like  happens  with  thc^e  native 
units  which  have  been  made  somewhat  dilfctiu  by  modilied 
functions  :  there  must  be  a  tendency  to  inheritance  of  acquired 
characters. 


M    reply  to  this  appeared  in  llie  April  i.ss'ie  of  the  Conlem- 
poratj  Review^  as  follows : — 


Injlucnce  on  Ptns^eny  of  a  Previous  Sire. 

This  is  the  last  of  the  an^uments  which  Mr.  Spencer  .advances 
against  the  posilicm  of  I'rofcssor  Weismann.  Alluding  t<»  the 
case  of  Lord  Morton's  mare,  he  represents  that  the  phenomenon 
which  it  serves  so  well  to  illustrate  viz.,  the  influence  of 
a  previous  sire  on  the  pro^tiiy  of  another  by  the  same  dam  is 
hopelessly  at  variance  with  the  theory  of  germ-plasm.  I  cannot 
quite  gather  the  explanation  which  he  would  give  of  this 
phenomenon,  further  than  that  in  some  way  or  another  it 
betokens  an  immediate  influence  of  the  hereditary  material  of 
the  male  on  the  body-tissues  ("  somatic  cells  ')  of  the  female. 
And  this  is  the  view  which  is  taken  of  the  phenomenon  by  th'j 
Lamarckians  in  gener.il.  Yet,  if  we  consider  all  that  such  an 
explanation  involves,  we  shall  lind  that  it  is  a  highly  complex 
explanation,  for  it  involves  the  following  chain  of  hypotheses:  — 
The  first  impregnation  affects  many,  if  not  all,  the  somatic 
tissues  of  the  mother  by  the  germinal  matter  of  the  father; 
these  tissues,  in  their  turn,  re-act  on  the  maturing  ova;  this 
action  and  reaction  is  such  that  when  one  of  the  ova  is  after- 
wards fertilized  by  a  different  sire,  the  resulting  offspring  more 


198    Afi  Examination  of  Weismannism. 


p. 

Vr 


^'^ 

j^i 


or  less  resemble  the  preceding  sire.  Unfortunately,  neither 
Wcisuiann  himself  nor  any  of  his  followers,  as  far  as  I  know, 
has  hitherto  published  an  opinion  on  the  subject ;  bui  I  imagine 
that  his  answer  would  be  three-fold.  First,  he  may  question 
the  fact.  Secondly,  even  admitting  the  fact,  he  may  say  it 
is  much  more  easy  to  ex[)!iiin  it  by  supposing  that  the  germ- 
plasm  of  the  first  sire  has  in  some  way  or  another  become 
partly  commingled  with  that  of  the  immature  ova,  as  well  as 
with  that  of  the  mature  one  which  it  actually  fertilizes;  and,  if 
so,  it  would  naturally  assert  its  influence  on  the  progeny  of 
a  subseciucni  sire.  Millions  of  spermatozoa  must  have  been 
playing  around  the  ovaries  after  the  first  copulation,  and  only 
one  of  them  was  needed  to  fertilize  the  mature  ovum.  It  is  not 
necessary  to  suppose  that  some  of  the  others  succeeded  in 
penetrating  any  of  the  immature  ova,  whilo  these  were  still 
embedded  in  the  substance  of  their  ovaries.  It  may  be  that  the 
life  of  "ids"  is  not  commensurate  with  that  of  their  containing 
spermatozoa.  After  the  latter  have  perished  and  disintegrated, 
their  ids  may  escape  in  thousands  of  millions,  bathing  in 
a  dormant  state  the  whole  surfaces  of  both  ovaries.  And,  if  so, 
it  is  conceivable  that  when  subsequent  ova  mature-  i.e,  come 
to  the  surface  of  their  ovaries  and  rupture  their  follicles — these 
dormant  ids  adhere  to  their  porous  walls,  through  which  they 
may  pass.  This  may  not  seem  a  very  probable  explanation; 
but,  at  any  rate,  it  is  a  less  improbable  one  than  that  on  which 
the  Neo-Lamarckians  would  found  an  argument  against  the 
continuity  of  germ-plasm.     F"or,— 

Thirdly,  is  it  not  literally  inconceivable  that  this  Nco- 
Lamarckian  explanation  can  be  the  true  one .''  Can  it  be 
seriously  contemplated  that  there  is  any  such  mechanism  as  the 
explanation  must  needs  assume .''  If  it  is  difficult  to  accept  such 
a  machinery  as  is  supposed  by  the  theory  of  pangenesis,  whereby 
every  cell  in  the  body  casts  off  "gemmules,"  which  are  the 
carriers  of  heredity  from  their  respective  tissues  to  the  germinal 
elements,  what  arc  we  to  say  of  such  a  machinery  as  the 
following : — A  machinery  which  distributes  through  the  body  of 
a  female  gemmules  from  the  disintegrated  spermatozoa  of  her 
mate ;  which  distributes  them  schxtivcly,  so  that  they  shall 
all  eventually  lodge  in  those  tissue-cells  of  the  female  which 


V\  •*. 


".,  "  ■"'   --r.tijfv 


Appendix  II. 


199 


correspond,  part  for  part,  with  the  tissiic-cclls  of  the  male  from 
which  they  were  originr  /  derived;  whic'.i  then  insures  that 
when  a  genimule  has  thus  reached  its  apjiropriatc  cell  in  the 
female  body,  it  will  thereupon  modify  the  pre-existing  gemmulcs 
in  that  cell,  so  that  when  they  arc  shed  and  go  to  form  tl>c 
germinal  contents  of  future  ova,  they  cnclow  the  latter  with  the 
hereditary  qualities  of  the  male  in  c|ucstion  ? 

Such,  it  seems  to  me,  is  a  fair  statement  of  the  whole  case  up 
to  date.  But  I  think  it  may  be  apposite  now  to  publish  the 
main  results  of  an  inquiry  on  which  I  have  been  engaged  for  the 
last  three  years. 

First  as  to  the  facts.  The  investigations  have  been  pursued 
on  three  different  lines:  (i)  1  raised  discussions  on  the  subject 
in  the  principal  breeders'  and  fanciers'  journals  of  this  country, 
and  also  of  America.  (2)  I  entered  into  private  correspondence 
with  contributors  of  the  largest  experience,  and  also  with  pro- 
fessional and  amateur  breeders,  fanciers,  ike,  who  addressed  me 
directly  on  the  subject.  (3)  .'  started  experiments  with  the 
varieties  which  these  inquiries  indicated  as  most  likely  to 
yield  positive  results.  At  present  nothing  need  be  said  with 
regard  to  these  experiments,  because  they  are  aoL  sufficiently 
matured.  But  it  is  desirable  to  state  the  general  upshot  of 
the  correspondence. 

The  principal  result  is  to  show  that  the  p!\cnomenon  is  of 
much  less  frequent  occurrence  than  is  ger-jrally  supposed. 
Indeed,  it  is  so  rare  that  I  doubt  whether  it  takes  place  in  more 
than  one  or  two  per  cent,  of  cases.  1  must  aild,  however,  that 
nearly  all  my  professional  correspondents  would  deem  this  an 
absurdly  low  estimate.  Most  of  them  are  quite  persuaded  that 
it  is  of  frequent  occurrence,  many  of  them  regard  it  as  a  general 
rule,  while  some  of  them  go  so  far  as  to  make  a  point  of  always 
putting  a  mare,  a  bitch,  &c.  to  a  good  jiedigret^  male  in  her  first 
season,  so  that  her  subsei|uent  i)rogeni:;s  may  be  benefited  by 
his  influence,  even  though  they  l)e  engendered  by  inferior  sires. 
But  I  am  certain  that  these  estimates  must  be  largely  discounted 
in  view  of  merely  accidental  resemblances,  and  still  more  on 
account  of  the  prevalent  belief  upon  the  subje(  t,  which,  where 
unquestioningly  entertained,  prevents  anything  like  a  critical 
estimate  beinji  formed. 


ii 


i«! 


200    An  Examination  of  Weisniannism. 

But  that  the  phenomenon  docs  occur  in  some  small  percentage 
of  cases  there  can  be  no  reasonable  doubt— as  a  result,  I  mean, 
of  analysing  the  hundreds  of  cases  which  have  now  been  sub- 
mitted to  me,  especially  with  regard  to  dogs.  One  thoroughly 
well  observed  case  occurring  among  pedigree  animals  is  worth 
any  number  of  slipshod  statements,  when  precedent  belief,  in- 
efficient isolation,  exaggeration  of  memory,  and  so  forth,  have  to 
be  allowed  for.  On  the  present  occasion  space  does  not  admit 
of  giving  such  special  instances,  so  I  must  ask  it  to  be  taken 
for  granted  that  my  evidence  is  enough  to  prove  the  fact  of  a 
previous  sire  asserting  his  influence  on  a  subsequent  progeny, 
although  this  fact  is  one  of  comparatively  rare  occurrence.  It 
may  be  added  that  1  have  failed  to  find  any  good  evidence  of 
its  ever  occurring  at  all  in  the  case  of  man.  For  although  I  have 
met  with  an  alleged  instance  of  a  white  woman,  who,  after  having 
borne  children  to  a  negro  husband,  had  a  second  family  to  a 
white  one,  in  which  some  negro  characteristics  appeared,  I  have 
not  been  able  to  meet  with  any  corroboration  of  this  instance. 
I  have  made  inquiries  among  medical  men  in  the  Southern 
States  of  America,  where  in  the  days  of  slavery  it  was  frequently 
the  custom  that  young  negresses  should  bear  their  first  children 
to  their  masters,  and  their  subsequent  children  to  negro  hus- 
bands ;  but  it  never  seems  to  have  been  observed,  according  to 
my  correspondents,  that  these  subsequent  children  were  other 
than  pure  negroes.  Such,  however,  was  not  the  same  case  as  the 
one  above  mentioned,  but  a  reciprocal  case ;  and  this  may  have 
made  a  difference.  If  any  reader  should  liapi)cn  to  know  of 
another  instance  where  a  negro  was  the  first  husband,  I  hope  he 
will  inform  me  as  to  the  result. 

It  has  hitherto  puzzled  me  why  the  phenomcncm  in  question, 
since  it  does  certainly  occur  in  some  cases,  should  occur  so  rarely 
as  the  above  inciuiiies  prove.  But  1  think  that  Mr.  Spencer's 
suggestion  on  this  point  is  a  valuable  one,  as  it  seems  to 
present  an  excellent  promise  of  solving  the  puzzle. 

This  suggestion,  it  will  be  remembered,  is  that  when  the  first 
sire  is  of  a  relatively  stable  and  also  of  a  markedly  different 
ancestral  stock  from  the  dam — e.g.,  of  a  different  species,  as  in 
the  case  of  Lord  Morton's  mare — there  will  be  most  likelihood  of 
his  inq)rcssing  his  ancestral  characters  on  the  progeny  of  the 


Appendix  II. 


20 1 


second  sire '.  And,  as  he  remarks,  it  would  indtxd  be  an 
extraordinary  coincidence  if  both  the  well-authenticated  cases 
given  in  the  College  of  Surgeons  Catalogue  should  have  con- 
formed to  his  explanation  by  mere  accident.  To  which  I  may 
add  that  the  supposition  of  such  an  accidental  coincidence  would 
seem  to  be  virtually  excluded  by  the  recent  occurrence  of  yet 
a  third  case  of  exactly  the  same  kind.  This  took  place  in  the 
Zoological  Gardens,  where  a  wild  ass  of  one  species  was  the 
previous  sire  to  a  foal  born  of  another  species  :  the  subsequent 
sire  was  of  the  same  species  as  the  mother,  and  his  foal,  lorn 
a  few  months  ago,  presented  an  unmistakable  resemblance  to 
the  other  species.  A  brief  account  of  the  particulars  is  given 
by  Mr.  Tegetmcier  in  the  Field  iox  December  14,  1892. 

So  much,  then,  for  the  facts.  As  regards  their  interpretation, 
it  certainly  seems  to  me  that  the  one  which  I  have  supposed  to 
be  given  by  VVeismann  is  less  difficult  of  acceptance  than  the 
one  which  is  given  by  the  Lamarckians,  as  we  have  seen  above. 
But  it  also  seems  to  me  that  the  latter  e.\i)lanation  is  not  the  on. y 
one  available  under  the  Lamarckian  hypothesis.  For,  even 
under  this  hypothesis,  there  is  no  need  to  assume  that  the  in- 
lluence  of  the  first  sire  is  exerted  on  all  the  somatic  tissues 
of  the  mother,  and  that  these  again  rellcct  this  influence  on 
the  ovum  which  is  afterwards  fertilized  by  the  second  sire. 
A  mechanism  that  could  effect  all  this  may  well  be  deemed  im- 
possible. l!ut  a  much  simpler  explanation  can  be  furnished 
by  the  Neo-Lamarckians,  on  lines  similar  to  those  upon  which 
I  have  supposed  that  Weismann's  explanation  woidd  run.  For, 
on  their  common  supposition  that  the  substance  of  heredity  is 
particulate,  it  matters  not  in  the  ptosent  connexion  whether  we 
suppose  the  particles  to  be  ids  or  gemnuiles.  Indeed,  it  is  more 
in  accordance  with  the  hypothetical  endowments  of  the  latter 
than  of  the  former,  that  they  should  be  capable  of  penetrating 
the  coats  of  an  ovum,  if  they  can  survive  tie  disintegration  of 
their  containing  spermatozoon.  Nevertheless,  thus  tar  it  does 
not  seem  to  me  that  any  theory  belonging  to  the  ...mily  of  pan- 
genesis can  gain  any  advantage  over  the  theory  of  germ-plasm, 

•  Readers  who  may  ha|ipen  to  he  ai(|uaiiile<l  wilii  De  Vrie'.' impoitmt 
essay  on  hticdity  will  jurceive  how  well  this  suggestion  (its  iu  wiih  his 
modification  of  Pangenesis. 


!t  t 


202    An  Exaviination  of  Weismannism. 

by  appealing  to  the  fact  of  a  previous  sire  sometimes  affecting 
the  progeny  of  a  subsequent  one.  The  case,  however,  is  widely 
different  if  we  turn  from  animals  to  plants,  thus. 

The  .idvantage  which  any  theory  of  gemmules  seeks  to  gain 
over  the  theory  of  germ-plasm  by  an  appeal  to  the  fact  in  ques- 
tion, consists  in  supposing  that  the  influence  of  the  previous  sire 
is  exercised  in  the  first  instance  on  the  somatic  cells  of  the  female. 
For  this  would  prove  that  the  germinal  elements  of  ^he  male  arc 
capable  of  communicating  their  hereditary  q'lal'iies,  not  only 
by  mixing  with  the  germinal  elements  of  the  female  (as  in 
ordinary  fertilization)  but  also  by  direc,  contact  with  the  general 
tissues  of  the  female.  And  this  agair.  would  prove  that  the 
funchunentai  postulate  of  the  theory  of  germ-plasm  is  erroneous 

i.e.,  the  postulate  of  the  continuity  of  germ-plasm,  or  of  its 
perpetual  restriction  to  a  "  sphere  "  of  its  own.  This,  as  all  who 
are  acquainted  with  the  literature  of  the  subject  will  at  once 
perceive,  would  be  a  serious  blow  to  the  whole  Weismannian 
system.  Jiut,  as  we  have  seen,  the  current  Lamarckian  inter- 
pretation of  the  fact  in  question  involves  the  supposition  of 
a  physiological  machinery  so  inconceivably  complex  that  instead 
of  serving  to  corroborate  the  theory  of  gemmules  (or  of  physio- 
logical units)  it  would  go  to  render  that  theory  incredible '. 


'  As  already  indicated,  I  cannot  gather  fiom  his  remarks  on  the  suliject 
which,  if  any,  of  the  allornative  interpretations  of  the  phenomena  that 
we  are  considering  Mr.  Spencer  adojits.  From  the  following  sentences 
it  would  appear  that  he  assi^-ns  yet  a  third  interi)retation,  and  this  as  the 
only  possible  one.  For  lie  says  of  these  phenomena:  "They  prove 
that  while  the  reprnductivc  cells  multiply  and  arrange  themselves 
duiing  the  e\()lutif)n  of  the  emhryo,  some  of  tlieir  germ-plasm  passes 
into  the  mass  of  somatic  cells  constituting  the  parental  hody,  and 
hecomes  a  permanent  component  of  it.  Further,  they  necessitate  the 
inference  tli;it  this  introduced  j,'erm-plasm.  everywhere  diffused,  is  some 
of  it  included  in  the  reproductive  celli  suhsecjuently  formed"  [iontcm- 
porary  Review,  March,  p.  4-;2^.  This  apiiears  to  mean  that  the 
influence  of  a  previous  siie  can  only  he  explained  t)y  supposing  that  Che 
developing  embryo  inoculates  the  somatic  tissues  of  its  mother  with 
hereditary  material  derived  from  its  fatlitr,  and  that  the  maternal  tissue 
afterwards  lellect  some  of  this  material  (or  its  inlhunce)  to  the  still 
unri]ie  ovarian  ova.  If  this  be  the  hyjiothesis  intended,  it  seems  to  me 
more  complex  than  any  of  the  thiee  which  I  have  sugj^ested.  Hut,  be 
this   as   it   m.ay,   we   ceitainly   cannot  agiee   that  such   an  hypothesis 


Appendix  II. 


203 


If,  however,  we  turn  lO  plants,  we  find  a  considerable  niimlier 
of  facts  which  unqucstionablv  demonstrate  the  only  point  which 
this  interpretation  has  been  adduced  to  suggest.  For  these 
facts  show  that,  in  not  a  few  cases,  the  germinal  matter  of 
pollen-grains  is  capable  of  asserting  its  influence  beyond  the 
ovules  to  the  somatic  tissues  of  the  ovary,  and  even  to  the  flower- 
stalk  of  the  mother  plant.  Here,  then,  we  have  simple  and  con- 
clusive evidence  of  the  material  of  heredity  exercising  a  direct 
influence  on  somatic  tissues.  How  this  well-known  fact  is  to  be 
met  by  the  theory  of  germ-plasm  is  a  question  which  does  not 
seem  to  have  thus  far  engaged  the  attention  of  Professor  Weis- 
mann,  or  of  any  of  his  followers.  For  particulars  touching  this 
phenomenon,  so  highly  important  in  its  relation  to  the  theory 
of  germ-plasm,  1  cannot  do  better  than  refer  to  the  eleventh 
chapter  of  Darwin's  work  on  the  *•  Variation  of  Animals  and 
Plants  under  Domestication." 

Again,  in  the  Contemporary  Rivieiv  for  May,  Mr.  Spencer 
wrote : — 

In  the  essay  to  which  this  is  a  p(u,t.'fript,  conclusions  were 
drawn  from  the  remarkable  lase  of  the  horse  and  quagga  there 
narrated,  along  with  an  analogous  case  observed  among  pigs. 
These  conclusions  have  since  been  confirmed.  I  am  much 
indel)ted  to  a  distinguished  corresjiondent  who  has  drawn  my 
attention  to  verifying  facts  furnished  by  the  offspring  of  whites 
and  negroes  in  the  United  States.  Referring  to  information 
given  him  many  years  ago,  he  says  : — "  It  was  to  the  effect  that 
the  children  of  white  women  by  a  white  father  had  been  re- 
peatedly observed  to  show  traces  of  black  blood,  in  cases  when 
the  woman  had  previous  connexion  with  [i.e.,  a  child  by|  a  negro." 
At  the  time  I  received  this  information,  an  American  was 
visiting  me  ;  and,  on  being  appealed  to,  answered  that  in  the 
United  States  there  was  an  established  belief  to  this  effect. 
Not  wishing,  however,  to  depend  upon  hearsay,  I  at  once  wrt-te 
to  America  to  make  int|uiries.  Professor  Cope  of  Philadeiphia 
has  written  to  friends  in  the  South,  but  has  not  yet  sent  me  the 

is  "proved  "  by  the  fatts,  or  tlint  the  latter  "ncctssilate  "  the  inference 
as  to  its  being  some  of  the  embryos  germinal  matter  which  enters  the 
unripe  ova. 


204    An  Examination  of  Weismanmsm. 


results.  Professor  Marsh,  the  distinguished  paleontologist,  of 
Yalo,  New  Haven,  who  is  also  collecting  evidence,  sends 
a  preliminaiy  letter  in  which  he  says :  "I  do  not  myself  know 
of  such  a  case,  but  have  heard  many  statements  that  make  their 
existence  prol}able.  One  instance,  in  Connecticut,  is  vouched 
for  so  strongly  by  an  acquaintance  of  mine,  that  I  have  good 
reason  to  believe  it  to  be  authentic." 

That  cases  of  the  kind  should  not  be  frequently  seen  in  the 
North,  especially  nowadays,  is  of  course  to  be  expected.  The 
first  of  the  above  quotations  refers  to  facts  observed  in  the  South 
during  slavery  days;  and,  even  then,  the  implied  conditions 
were  naturally  very  infrequent.  Dr.  W.  J.  Youmans  of  New  York 
has,  on  my  behalf,  interviewed  several  medical  professors,  who, 
though  they  have  not  themselves  met  with  instances,  say  that 
the  alleged  result,  described  above,  "  is  generally  accepted  as 
a  fact."  13ut  he  gives  me  what  I  think  must  be  regarded  as 
authoritative  testimony.  It  is  a  quotation  from  the  standard 
work  of  Professor  Austin  Flint,  and  runs  as  follows : — 

A  neculiar  and,  it  seems  to  me,  an  iiicxi)licable  fact  is,  that  previous 
pregnancies  have  an  influence  upon  oflsiiring.  Tliis  is  well  known  to 
brctilers  of  animals.  Jf  pure-blooded  mares  or  bitches  have  been  once 
covered  by  an  inferior  male,  in  sulisequent  fecundations  the  young  are 
likely  to  partake  of  the  character  of  the  first  male,  even  if  they  be  after- 
wards bred  with  males  of  unimpeachable  pedigree.  What  the  mechanism 
of  the  influence  of  the  (irst  conception  is,  it  is  impossible  to  say;  l)Ut  the 
fact  is  incontestable.  The  same  influence  is  observed  in  the  human 
subject.  A  woman  may  iiave,  l)y  a  second  husband,  children  who 
resemble  a  former  hus])an'l,  and  this  is  particulaily  well  marked  in 
certain  instances  by  the  colour  of  the  hair  and  eyes  A  white  woman 
who  has  had  children  by  a  negro  may  subsequently  bear  children  to 
a  while  man,  these  children  presenting  some  of  the  unmistakable  peculi 
arities  of  the  negro  race  '. 

Dr.  Youmans  railed  on  Professor  Flint,  who  remembered 
"investigating  the  subject  at  the  time  his  larger  work  was 
written  |'  alxive  is  from  an  abridgment],  and  said  that  he 
had  nevei  i     -^d  the  statement  questioned." 

Some   day  ^   before   I   received  this  Utter  and  its  contained 

1  "A  Text  Book  of  Human  l'h\  siology."  By  Austin  Hint,  M.D.,  LL.  D. 
Fouith  edition.     New  York:   D.  Apjili-ton  &  Co.      i8SS.     I'age  797. 


Appendix  II. 


205 


quotatinn,  the  rem  niljiancc  of  a  rcm;iik  I  litard  many  years 
ago  concerning  clogs,  led  to  the  incjuiry  wluther  they  furnished 
analogous  evidence.  It  occurred  to  me  that  a  friend  who  is 
frequently  appointed  judge  of  animals  at  agricultural  shows, 
Mr.  Fookes,  of  Fairfield,  I'ewsey,  \\  iltshire,  might  know  some- 
thing about  the  matter.  A  letter  to  him  brougiit  various 
oonfirmatory  statements.  From  one  "  who  had  bred  dogs  for 
many  years''  he  learnt  that    - 

It  is  a  well-known  and  aihnitlcd  fact  that  if  a  hitch  has  two  littcis 
by  two  dilTcient  dogs,  the  cliaracter  ol  the  liiit  fallier  i?  sure  to  be 
perpetuated  in  any  litters  slie  may  aftei wards  have,  no  matter  how 
piuc-breil  a  dog  may  be  the  begetter. 

After  citing  this  testimony,  Mr.  Fookes  goes  on  to  give  illustra- 
tions known  to  himself. 

A  friend  of  mine  near  tliis  had  a  very  valual>le  Dachshund  bitch, 
which  most  unfortunately  had  a  litter  by  a  stray  sheep-dog  The  next 
yenr  her  owner  sent  her  on  a  vi  it  to  a  ])ure  Daclishuiid  dog.  but  the 
[iroduce  look  ((uite  as  nuich  of  the  llr^t  lather  as  the  -ecoiul.  and  the 
next  year  he  sent  her  to  another  Duchshuml  with  the  same  result. 
Anoliicr  case:  — .\  friend  of  mine  in  Devizes  had  a  litter  of  pujipies, 
unsought  for,  by  a  setter  from  a  favourite  ])f)inter  bitch,  and  after  this 
she  never  bred  any  true  pointers,  no  matter  of  what  the  paternity  was. 

These  further  evidences,  to  which  Mr.  Fookes  has  since 
added  others,  render  the  general  conclusion  incontestable. 
Coming  from  remote  places,  from  those  who  have  no  theory  to 
support,  and  who  are  some  of  them  astonished  by  the  unexpected 
phenomena,  the  agreement  dissipates  all  doubt.  In  four  kinds 
of  mammals,  widely  divergent  in  their  natures  man,  horse,  dog, 
and  pig — we  have  this  same  seemingly  anomalous  kind  of 
heredity  made  visible  under  analogt)us  conditions.  We  must 
take  it  as  a  demonstrated  fact  that,  during  gestation,  traits 
of  constitution  inherited  from  the  father  produce  effects  upon 
the  constitution  of  the  mother  ;  and  tliat  these  communicated 
effects  are  transmitted  by  her  to  subsequent  oftspring.  We  are 
supplied  with  an  absolute  disproof  of  I'rolessor  Weismann's 
doctrine  that  the  reproductive  cells  arc  independent  of,  and 
uninfluenced  by,  the  somatic  cells  ;  and  tbeie  disapjiears  abso- 
lutely the  alleged  obstacle  to  the  transmission  of  actiuired 
characters.  .  .  . 


2o6    An  Examination  of  Weismannism. 


%m 


■1  :.;:■< 


Biil 


m 


There  is  one  other  passage  in  Dr.  Romanes'  criticism — that 
conccrninj;  the  influence  of  a  previous  sire  on  progeny — which 
calls  for  comment.  He  sets  down  what  he  supposes  Weismann 
will  say  in  response  to  my  argument.  "  First,  he  may  question 
the  fact."  Well,  after  the  additional  evidence  given  above, 
I  think  he  is  not  'ikely  to  do  that ;  unless,  indeed,  it  be  that 
along  with  readiness  to  base  conclusions  on  things  "it  is  easy 
to  imagine  "  there  goes  reluctance  to  accept  testimony  which  it 
is  difficult  to  doubt.  Second,  he  is  supposed  to  reply  that  "  the 
germ-plasm  of  t^e  first  sire  has  in  some  way  or  another  become 
partly  commingled  with  that  of  the  immature  ova";  and 
Dr.  Romanes  goes  on  to  describe  how  there  may  be  millions 
of  spermatozoa  and  "thousands  of  millions  "  of  their  contained 
"  ids  "  around  the  ovaries,  to  which  these  secondary  effects  are 
due.  But,  on  the  one  hand,  he  docs  not  explain  why  in  such 
case  each  subsequent  ovum,  as  it  becomes  matured,  is  not 
fertilized  by  the  sperm-cells  present,  or  their  contained  germ- 
plasm,  rendering  all  subsequent  fecundations  needless  ;  and,  on 
the  other  hand,  he  does  not  explain  why,  if  this  does  not  happen, 
the  potency  of  this  remaining  germ-plasm  is  nevertheless  such 
as  to  affi'ct  not  only  the  next  succeeding  offspring,  but  all 
subsequent  offspring.  The  irreconcilability  of  these  two  impli- 
cations would,  I  think,  sufificiently  dispose  of  the  supposition, 
even  had  we  not  daily  multitudinous  proof  that  the  surface  of  a 
mammalian  ovarium  is  not  a  sperm-atheca.  The  third  difficulty 
Dr.  Romanes  urges  is  the  inconceivability  of  the  process  by 
which  the  germ-plasm  of  a  preceding  male  parent  affects  the 
constitution  of  the  female  and  her  subsequent  offspring.  In 
response,  I  have  to  ask  why  he  piles  up  a  mountain  of 
difficulties  based  on  the  assumption  that  Mr.  Darwin's 
explanation  of  heredity  by  "Pangenesis"  is  the  only  available 
explanation  preceding  that  of  Weismann?  and  why  he  presents 
these  difficulties  to  me  more  especially,  deliberately  ignoring 
my  own  hypothesis  of  physiological  units.?  It  cannot  be  that 
he  is  ignorant  of  this  hypothesis,  since  the  work  in  which  it  is 
variously  set  forth  ("  Principles  of  Biology,"  §§  66-97)  is  one 
with  which  he  is  well  acquainted :  witness  his  "  Scientific 
Evidences  of  Organic  Evolution " ;  and  he  has  had  recent 
reminders  of  it  in  Weismann's  "Germ-plasm,"  where  it  is 


\%A\ 


'~n 


Appendix  II. 


207 


repeatedly  rcfeneil  to.  Why,  then,  docs  he  assume  that 
I  abandon  my  own  hypothesis  and  adopt  that  of  Darwin,  there- 
by entangling  myself  in  difficulties  which  my  own  hypothesis 
avoids  ?  If,  as  I  have  argued,  the  germ-plasm  consists  of 
substantially  similar  units  (having  only  tiiose  minute  differences 
expressive  of  individual  and  ancestral  differences  of  structure), 
none  of  the  complicated  requirements  which  I)r,  Romanes 
empii     ises  exists,  and  the  alleged  inconceivability  disappears. 

To  this  I  responded,  in  the  Coniemporary  Raiiw  for 
June  :— 

With  regard  to  the  influence  of  a  previous  sire,  I  ventured 
in  my  article  to  show  that,  even  supposing  it  to  be  a  fact, 
the  phenomena  concerned  would  not  constitute  any  valid 
evidence  against  Weismann's  theory  of  germ-p'asm,  and,  of 
course,  still  less  would  "  they  prove  that  while  the  reproductive 
cells  multiply  and  arrange  themselves  during  the  evolution 
cf  the  embryo,  some  of  their  germ-plasm  passes  into  the  mass 
of  somatic  cells  constituting  the  parental  body,  and  becomes 
a  permanent  component  of  it,"  with  the  result  that  the  phe- 
nomena in  question  "  are  simply  fatal  to  Weismann's  hypothesis." 
For  a  much  simpler  and  more  probable  explanation  is  to  be 
found  in  supposing  that  the  unused  germ-plasm  of  the  first  sire 
may  survive  the  disintegration  of  its  containing  spermatozoa  in 
the  Fallopian  tubes  of  the  female,  and  thus  gain  access  to  the 
hitherto  unripe  ova  directly^  instead  of  first  having  to  affect  the 
whole  maternal  organism,  and  then  being  rcjlt-rted  from  it  to 
them.  I  showed,  at  some  length,  how  immensely  complex  the 
mechanism  of  any  such  process  would  necessarily  have  to  be ; 
and  for  the  purposes  of  exposition  I  employed  the  terminology 
of  Darwin's  theory  of  Pangenesis.  Mr.  Spencer  now  says: 
"  In  respcmse,  I  have  to  ask  why  he  [I]  piles  up  a  mountain 
of  difficulties  based  on  the  assumption  that  Mr.  Darwin's 
explanation  of  heredity  by  'Pangenesis'  is  the  only  available 
explanation  preceding  that  of  Weismann  ?  and  why  he  presents 
these  difficulties  to  me  more  expecially,  deliberately  ignoring 
my  own  hypothesis  of  physiological  units.'"  Now  my  answer 
to  this  is  very  simple.  I  do  not  hold  a  brief  for  W'eismann. 
On  the  contrary,  I  am  in  large  measure  an  opponent  of  his 


u    I 

r. 


i ,  i  ir 
ilil 

III 


r* 


208    ^«  Iixaininafion  of  Weisniaiinism, 

views ;  and  my  only  object  in  pul)lislii}ii:j  my  previous  article 
was  to  save  the  theory  of  usc-inlicritance  from  what  seemed  to 
me  the  weaker  parts  of  Mr.  Spencer's  ad\ocacy,  while  thus  all 
the  more  eniphasizin.sf  my  acceptance  of  its  stronger  parts. 
Therefore,  the  impression  which  he  seems  to  have  gained  from 
my  attempts  at  imi)artiality  is  entirely  erroneous.  Far  from 
"deliberately  i;4noring"  any  of  his  arguments  or  hypotheses 
whirh  seemed  to  meat  all  available  on  the  side  of  use-inherit- 
ance, I  everywhere  endeavoured  tf)  make  the  most  of  them. 
And,  as  re.q^ards  this  particular  instance,  I  expressly  used  the 
term  *' gemnuiles,"  instead  of  "  johysiological  units,"  simply 
because  I  could  not  see  that,  as  far  as  my  "mountain  of  dif- 
ficulties'* was  concerned,  it  could  make  one  atom  of  difference 
which  term  I  emi)loyed.  It  now  appears,  however,  that,,  in 
Mr.  Spencer's  opinion,  there  is  some  very  great  difference. 
For,  while  he  allows  that  the  "mountain  of  difficulties"  which 
I  have  "piled  up"  against  his  interpretation  of  the  alleged 
phenomena  would  be  valid  on  the  supposition  that  the  ultimate 
carriers  of  heredity  arc  "gemmules,"  he  denies  that  such  is  the 
case  if  we  suppose  these  ultimate  carriers  to  be  "  physiological 
units."  For  this  statement,  however,  he  gives  no  justification  ; 
and,  as  I  am  unable  to  conceive  wherein  the  difference  lies, 
I  sincerely  hope  that  in  any  subsequent  editions  of  his  pamphlet 
Mr.  Spencer  will  furnish  the  requisite  explanation.  Cdadly 
substituting  the  words  "physiological  units"  wherever  I  have 
used  the  word  "gemmules,"  I  am  genuinely  anxious  to  ascertain 
how  he  would  overcome  the  "mountain  of  difficulties"  in 
question.  For  I  do  not  regard  the  subject  as  one  of  mere 
di;ilectics.  It  is  a  subject  of  no  small  importance  to  the  general 
issue,  Weismann  versus  Lamarck  ;  and,  therefore,  if  Mr.  Spencer 
could  show  that  the  phenomena  in  question  make  exclusively  in 
favour  of  the  latter,  as  he  alleges,  he  might  profitably  inform  us 
in  what  way  he  supposes  them  to  do  so. 

In  conclusion,  I  would  like  to  take  this  opportunity  of  ex- 
plaining that  my  former  article  was  written  in  Madeira,  where 
I  did  not  receive  a  copy  of  Weismann's  most  recent  work, 
entitled  The  Germ-plasm,  until  the  Contemporary  Re7new  for 
April  was  being  printed  off.  Thus,  I  was  not  then  aware  that  in 
this   work  Professor  Weismann  had  fully  anticipated  several 


Appendix  II. 


209 


of  Mr.  Spencer's  criticisms— including  this  matter  of  the 
influence  of  a  previous  sire.  Here  he  adopts  exactly  the  position 
which  in  my  article  I  surmised  that  he  would  ;  so  that,  to  all 
who  have  read  The  Germ-plasm,  it  must  have  appeared  that 
I  was  prophesying  after  the  event.  Hence  the  need  of  this 
explanation. 

Lastly,  in  the  same  issue  of  the  Contemporary  Rein'eiv, 
Mi.  Spencer  explained: — 

Mr.  Darwin's  hypothesis  of  Pangenesis  implies  not  only  that 
the  reproductive  cell  must  contain  numerous  kinds  of  gemmules 
derived  from  different  organs,  but  that  the  numbers  of  these 
gemmules  must  bear  to  one  another  something  like  the  pro- 
portions which  the  originating  organs  bear  to  one  another  in 
size.  The  conception  involves  many  different  /diiiis,  whose 
numbers  are  in  many  different  proportions,  and  I  supposed  the 
difficulty  alleged  was,  that  for  the  influence  of  a  previous  sire  to 
be  communicated  from  the  growing  fcetus  to  the  mother  would 
imply  not  only  the  transfer  of  the  various  kinds  of  gemmules 
derived  from  him,  but  also  maintenance  of  their  numerical 
proportions,  and  that  again  these  gemmules,  diffused  throughout 
the  maternal  system,  would  have  to  be  transferred  in  these  pro- 
portions to  the  subsequently  formed  ova.  No  such  difficulties 
arise  if  the  units  conveying  hereditary  characters  are  of  one 
kind  only. 

From  this  it  is  apparent  that  Mr.  Spencer  has  misunder- 
stood "  the  difilculty  alleged,"  and  that  the  desired  explanation 
is  not  yet  forthcoming.  I  did  not  say  anything  about  "  kinds  " 
or  "  proportions  "  of  the  carriers  of  heredity ;  my  difTiculty 
is  to  conceive  of  any  mechanism  whereby  these  carriers  can 
first  directly  influence  the  somatic-cells  of  the  mother,  and 
then  indirectly  reflect  this  influence  upon  her  germ-cells. 
Also,  I  cannot  see  any  obvious  necessity  for  the  intervention 
of  the  "  embryo  "  in  the  process. 


It ,  ..' 


"It 

.  lit       * 


GLOSSARY. 


-*♦- 


Acquh'ed  character.._.S«  Somato^cnctic  characters. 
Amphigony  iHackel).-SexuaI  reproduction 

AmphimixiscWeismann).-Tl,emin,Min,M.fthcla.reditary«„bs^^^^^^^ 
or  two  individuals  in  an  act  of  sexual  union 

Ancestral  Kerm-plosm.— iVt'  ji  123 

,crm  els  contanunfj  the  potentiality  of  the  a.iult   or,^,nism,  tnU 

gi  'Wtls,  &c.    which  develop    into    the  j.arent    form.       There  are 
many  forms  of  asexual  reproduction. 
Atavi«m._The  al>r.ormal  occurrence  in  existing,  species  of  character, 

rt//t^;  Uarwin,  2nd  ed.,  Part  I,  p.  94. 

Biophore.— 5'tv  p.  123. 

Blastogenetio  characters.-.9..  IMasmo,r,nefic  characters. 

Calyx._The  outermost  eoverin^^  of  the  (lower,  which  protects  it  l.efore 
opening.     Its  position  and  precise  function  vary 

Cell  nucleus  A  spherical  or  ovoid  body  embe,lde<l  in  the  cell  proto- 
plasm, whtch  has,mpor.ant  functions  in  cell  division  ..nd  in  re  o- 
duction.      t  consists  of  chromatin  and  acluomatin.     There  are        n 

w  a  ::t:;:t:r^"' ^^'^'^^ -'"-^''^ '--■---^-- 

Cessation  of  Selection  (Romanes\-.S-..  I'anmixii 
Chromatin  threads.-Immediately  before  a  cell  diiides  the  nucleus  is 
r^olved  into  chromatin  hbres  or  threads  and  an  achromatin  ma  i 
Ihese  chrcHnatin  fibres  are  then  marshalled  into  either  rods  or  1  ^  ; 
&c  a.  the  division  of  the  cell  proceeds  ;see  Danvin  and  after 
^anon^,  fjgs  36,  37,  and  38^.  Sul.sec,uent  cban.H.  in  the  thn .^  s 
conclude  the  division   for  a  description  of  which  ctnsult  the  ac;;:.!: 

Chromosomes.— 5^^  Chromatin  thieads. 

Pa 


.'212 


Glossary, 


Compositae. — Plants  in  which  the  inflorescence  consists  of  numerous 
small  flowers  brought  together  into  a  dense  head,  the  base  of  which 
is  enclosed  by  a  common  envelope  (e.g.  the  Daisy,  Dandelion,  &c.). 

Congenital  characters. — See  Plasmogenetic  characters. 

Conjugation. — This  term  is  applied  to  a  process  observed  in  the 
Protozoa  (q.  v.",  which  seems  to  correspond  to  the  sexual  reproduction 
of  the  Metazoa  (q.  v.).  The  majority  of  the  I'rotozoa  cannot  long 
continue  to  reproduce  themselves  ascxually  without  becoming 
degenerate,  or  rather  without  becoming  altogether  extinct.  Two 
individuals  (as  a  rule)  consequently  unite  either  temporarily  or 
permanently.  In  the  former  case,  an  exch.mge  of  material  is  eflectcd  ; 
and  in  the  Intter,  complete  fusion  takes  place. 

Correlation. — The  normal  coiiiciiicnce  of  one  phenomenon,  character, 
&c.,  with  another. 

Cytoplasm. — See  pp.  30  and  33. 

Determinant. — Sce\*.  123. 

Ectoblast. — Syn.  of  cj)ibiast  and  ectoderm.  The  general  result  of  the 
division  of  a  fertilized  ovi;m  is  a  two  layered  ball  of  cells  (a  gastrula). 
The  outer  l.iyer  is  called  the  eotobl  isl  and  the  inner  layer  the  cnto- 
blast.     (See  J)a>i.vin  and  after  Dariuin,  p.  137  et  seq.). 

Embryology. — [fence  embryogenesis,  &c.  The  study  of  the  develop- 
ment or  the  early  growth  of  thf  individual. 

Entoblaat. — Syn.  of  hypobl.ast  and  endoderm.     See  Ectoblast. 

Epigenesis  (Harvey). — The  theory  that  organisms  are  formed  by  the 
development  of  the  egg  itself,  and  not  by  tiie  ex[)ansion  of  a  miniature 
within  the  egg  (prelormation). 

Fallopian  Tubes. — The  tubes  through  which  the  spermatozoa  pass  to 
effect  iertilizalion,  and  through  which  the  ova  pass  from  the  ovary  to 
the  uterus. 

Fission. — .Syn.  of  fissiparous  separation.  Tiie  breaking  into  two 
(without  karyokinesis— q.  v.^  of  a  cell,  wliich  Ii.is,  by  overgrowth, 
disturbed  its  physiological  etjuilibrium.  This  process  is  almost 
meclianical. 

Formative  material. — See  p.  f/). 

Gemmation. — That  form  of  asexual  reproduction  known  as  budding. 

Gemmules  (Darwin). — Minute  granites,  formed  liy  the  division  of  the 
general  body-cells,  which  are  supposed  to  I)e  dispersed  tin  oughout  the 
entire  system.  These  themselves  multiply  by  division,  and  are 
collected  from  all  parts  of  the  body  to  constitute  the  sexual 
elements. 

Germ-plasm. — See  p.  32. 

Hydroids.  Belong  to  a  division  (Hydrozoa)  of  the  stinging-animals 
or  Coelenlcrata.  They  occur  both  in  tiie  sea  and  in  fresh  water,  and 
are  solely  polypoid  (i.e.  tubulai  and  tentacled). 


Glossary. 


213 


Hydromedusae. — Also  Ilydrozoans.     Ilydroid   colonies  with  special 
sexually  reproductive  persons,  which  are  often  liljeraled  as  floating 
bells  or  discs. 
Idio-plasm  ,A  and  B). — See  pp.  31  and  32. 
Ids. — See  p.  123. 

Invertebrata. — Animals  with  a  dorsal  lieart  and  without  a  backbone. 
Karyokinesis.—  The  chan_t,'es  wiiich  are  oljserved  in  the  nucleus  both 

immediately  before  and  after  cell  division.     See  Chromatin  tlireads. 
Lamarckian    factors.     See    Somatogenetic    characters.      Also   Neo- 

Lamarckians. 
Metaphyta. — Multicellular  plants  (q.  v.). 
Metazoa. — Multicellular  animals  (q.  v.). 

Micellae  (Niigeli). — See  Molecules,  with  which  they  are  identical. 
Microsomata. — The  protoplasm  of  certain  vej^etable  cells  is  in  places 
characterized  by  the  pr;sence  of  minute  corpuscles,  wluch  may  be 
rei^ardcd  as  part  of  the  proto])lasm,  and  are  certainly  of  a  j)rotoplasmic 
nature.     These  are  termed  Microsomata. 
Molecules  (Weismann).  — .S"^^  p.  122. 

Multicellular   orgauisms. — Ori^anisms  composed    of  many  cells,  as 
distinguished  from  the  Unicellular  org.inisms,  where  each  individual 
is  constituted  of  only  one  cell. 
Natural    Selection. — Survival    of    the     Fittest    in    the   struggle    for 
existence.     For  a  full  account  of  the  process  see  Danvin  and  after 
Darivin,  p.  251  el  seq. 
Neo-Darwiuiana. — Those   who    believe    that   Natural   Selection   has 
been  the  only  modilying  intliience  in  the  evolution  of  species,  and 
that    the    material     for    its    action    has    been    only    piasmogenetic 
characters  (q.  v.). 
Neo-Lamarckians. — Those  who  hold  that  organic  evolution  has  Ijeen 
effected  solely  by  means  of  the  occurrence  and  preservation  (inheritance) 
of  somatogenetic  characters  ((|.  v.  . 
Nuclear  Thread  or  Loops.-  .SVc- Chromatin  threads. 
Nucieo-plasm. — See  pp.  30  and  32. 
Nucleus. — See  Cell  nuc'  us. 
Nutritive  congenital  charactci's. — See  p.  64. 
Ontogenetic  grades.-   See  ■     •  i. 
Ontogeny. — The  life  history  or  tlie  individunl,  as  distinguished  from  the 

ancestral  history  (*f  the  race  ( I'hylogeny  i. 
Ova. — i-ggs — the  product  of  the  lemale  leproductivc  gland  (ovary  or 

ovarium). 
Ovule. — The  seed  in  its  earliest  condition. 

Pangenesis  iDarwin  .      The  th<  ory  of  Heredity  by  gemmules  ((|.  v.). 
Panmixia    < 'Weismann'). — The    cf)ndition    ol    fne    intercrossing,  i.e 
where  Natural  Selection  \,q.  v.)  cannot  act. 


214 


Glossary. 


PI 


Parthenogenesis. — A  degenerate  form  of  sexual  reproduction,  in  which 
the  egg  develops  without  having  been  fertilized  by  the  male 
element. 

Phylogen: . — The  ancestral  history  of  the  race,  as  distinguished  from 
the  life  history  of  the  individual  (Ontogeny). 

Physiological  Units  (Spencer). — Special  units  which  it  is  inferred 
a  plant  or  animal  of  any  species  is  made  up  of,  and  in  all  of  which 
dwells  the  intrinsic  aptitude  to  aggregate  into  the  form  of  tiiat 
sjiecies. 

Plasma. — The  constituent  material  of  cells,  e.  g.  gerniplasma  (of  sexual- 
cells),  somatoplnsma  (of  body-cells). 

Plasmogenetic  characters. — Variations  due  to  admixtures  of  germ- 
nlasm  in  acts  of  sexual  fertilization  (and  therefore  present  at  birth), 
as  d'.stiiiguished  from  somatogenetic  characters — variations  which 
have  been  acquired  independently  of  germ-plasm.  See  Somato- 
genetic characters. 

Polar  bodies. — Hefore  an  egg  is  fertilized  the  nucleus  moves  tovards 
the  jieriphery  and  divides  twice.  The  two  cells  that  are  thus 
formed  are  the  polar  bodies.  The  extrusion  of  polar  bodies  is 
probably  universnl  among  animals,  but  only  one  polar  body  is 
extrui'ed  from  |iarthenogcnetic  ova.  See  Darivin  and  after  Darwin, 
pp.  125  and  I  26. 

Preformation. — The  old  conjecture  (1672 — M:dpiglii)  that  the  de- 
velopment of  nn  embryo  was  merely  tin-  expansion  or  unfolding  of 
a  miniature  of  the  adult  within  the  egg. 

Protophyta. — Unicellular  plants  (q.  v.). 

Protoplasm. — Living  matter. 

Protozoa. — Unici  llular  animals   q.  v.). 

Representative  Congenital  characters. — See  p.  65. 

Reversion. — See  Atavism. 

Rudimentary  Organs. — Usually  considered  a  synonym  of  the  term 
"vestigial  characters,"  and  is  the  name  under wiiich  are  included  all 
those  organs  which,  either  from  having  become  us  less  or  from  other 
causes,  have  been  much  reduced  in  size,  e.g.  the  muscles  o<"  the 
external  ear  in  man  (see  Darvun  and  after  l\inuin,  p.  76),  &c. 
Latterly  the  former  expression  has  been  used  to  describe  organs  in 
process  of  development  (e.g.  the  electric  organ  of  the  skate — loc.cit.y 
p.  365  et  setj.  ,  whilst  the  latter  is  made  to  embrace  all  those  organs 
in  process  of  elimination. 

Soma. — A  general  term  desciiptive  of  the  whole  mass  of  the  body-cells 
of  an  organism. 

Somatic-idio-plasra. — See  p.  3a. 

Somatogenetic  characters. —  Ch  .acters  acquired  by  the  soma  (i.e. 
variations  acquired  alter  birth  by  the  action  of  the  environnunt),  as 


1* 


I* 


Glossary. 


215 


distinguished  from  characters /m///,.-,/ and  potentially  present  from 
the  first  by  a  union  of  two  masses  of  gcrm-plaMn-plasmuLrenetic 
characters  (q.  v.\ 

Soraato-plasm. — See  p.  32. 

Specialized  congenital  characters.— 5^^  p.  65. 

Spermathecae.-Ori,rans  for  the  storing  of  the  seminal  fluid  received  in 
copulation. 

Spermatogenesis.— The  precise  development  of  spermatozoa 
Spermatozoa.-'l'he  essential  elements  in  the  male  seminal  fluid,  and 

secreted  bv  the  testis— the  male  reproductive  gland. 
Stirp  (Qalioi;.  -See  p.  58. 
Telegcn.v.     0  141. 

Unicellu)      O,  .    ...asms.-Organisms  composed  of  a  sin-le  cell  only 

as  distu!gu'.,ied  Irom  those  consisting  of  aggiegations  of  cell.-' 

Multicellu'iar  organisms. 
Vertebrj,ta.— Animals  with  a  backbone  and  a  ventral  lieait. 
Vestigial  Orgars.  -Ac  Rudimentary  organs. 
Xeuia. — See  p.  141. 


:  m_ 


!/n 


'lii 


INDEX. 


Acquired  characters,  definition  of, 
p.  5  ;  inheritance  of,  6, 15.  49,  57, 
f>o,  67,69,  71,  81,  83-84,  93- 
9f».  104,  107,  iio-iii,  127, 
173.  ^^  ^eq.  ;  Gallon  on  inheri- 
tance of,  62,  106. 

Adaptive  development,  Weismann 
on,  19. 

Algae,  De  Vries  on  the  chromato- 
phores  of,  83.  in. 

Amphipony,  the  cause  of  indi- 
vidual liereditary  variation,  91, 

lOO-IOI. 

Amphimixis,  see  Sexual  propaga- 
tion. 
Ancestral  germ-j>lasm,  123. 
Atavism,  3,  91,  lo;;. 

B. 

Bary,  De,  on  Weismann 's  theory, 

152- 
Basidiomycctes,  90. 
l^egonia,  rtgeneratiun  in,  4,  52. 
liiophorcs,  123. 
Body-cells,  and  gcrm-cells,  29. 
Brooks,  theory  of  heredity,  2. 
Bud- variation,  90,  94,  96,'9S-99  ; 

Weismann    on,    95,   97,     ,6,  ; 

Pntz  Miillcr  on,  95. 
Butterflies,    climr.'ic'  varieties    of 

and    Weismann's    theory,     67 

68,  137-128.  ' 


Candolle,  De,  on  inheritance  of 
acquired  characters  in  jdants,  (,3. 

"Carriers  of  Heredity,"  32,  j,8, 
70,  78,  122. 


Cessation   of  Selection,   see  Pan- 
mixia. 
Chromntophores,  of  Algae,S3, 1 1 1. 
Compositae,  pollen  of,  5. 
Congenital    variations, '  definition 
of,    5;  inheritance   of,  6,   no; 
sexual    propagation    the   cause 
of,  n  ;  Darwin  on,  13;  oris^in 
°f'    23,   2,ii,   100,  102;  nutritive 
congenital  changes,  64;  exam- 
ples   of,   64;    specialized    con- 
genital changes.  65  ;  representa- 
tive   congenital    changes,     65 ; 
(ialton  on,  134. 
Continuity    of    germ-plasm,     see 

Germ  plasm. 
Crustacea,  and  the  inheritance  of 

acquired  characters,  94. 
Cuitmgs,  and  bud-variation,  98. 
Cylisus  cuiami,  grafting  of,  127. 

D. 

Darwin,  Charles, and  Pangenesis, 
2,  2O;  arguments  in  favour  of 
pangenesis,  3,  59;  on  the  cause 
of  congenital  v^iriations,  i^; 
comparison  of  his  theory  "of 
heredity  with  that  of  Weis- 
mann,    52,    55,    73,    92,    105- 

'°''»  115-  '.^3.  173  et  seq.;  on 
germ  and  somatic-cells,  76 ;  on 
tile  influence  of  pollen  upon 
somatic  tissues,  79-.S0;  on  graft- 
hyt.ridization,  S3  ;  on  t,u(l- 
variation,  95  ;  on  the  causes  of 
.  yaiiation,  102,  161  ;  on  the 
iniierilance  of  acquired  charac- 
ters, 107,  ni-n2;  on  .\enia, 
I.J4;  oii  sexual  union,  154. 


2l8 


Index, 


Death,  Wcismann  on  the  origin  of, 

S,  lo  ;  in  plints,  lo. 
Determinants,  1 23. 
Direct  action  of  environment,  on 

unicellular  organisms,  15,  23. 

E. 

Elsberg,  theory  of  heredity,  2. 
Environment,  direct  aciion  of  o' 

Protozoa,  15. 
Evolution,  see  Organic  evolution. 

F, 

Flint,  Prof.  Austiu.on  Telegony, 
204. 

Pocke,  on  Xenia,  141,  144. 

"  Formative  material,"  and  germ- 
plasm,  56. 

Fungi,  Prof.  Vines  on  Basidiomy- 
cetes,  yo. 


Galton,  Francis,  theory  of  here- 
dity (stirp),  2  ;  and  VVeismann's, 
51)  5^-.=^9.  69,  73,  92,  105-106, 
108,  115,  129,  130  et  sei],\  on 
gemmules,  60  ;  on  inheritance 
of  acquired  characters,  <'>2,  Txj, 
107;  nnd  stability  of  the  ma- 
tei  i  f'.isis  of  heredity,  63  ;  on 
origin  of  sexual  reproduction, 
103,  167. 

Giirtner,  on  Malva,  80 ;  on  in- 
heritance of  acquired  characters 
in  plants,  93. 

Gemmules,  2  ;  Darwin  on  the 
si/e  of,  4  ;  and  gerni-plasm,  52, 
55,  58,  92,  105;  and  stirp,  58; 
Galton  on,  60. 

Generative  cells  of  the  Ilydro- 
medusae,\Veismnnn  on,  71.  109  ; 
example  of  continuity  of  germ- 
plasm,  72-73. 

Germ-cells,  and  body-cells,  29, 
7.'i~77  ;  nucleo-plasm  of,  30; 
number  of  43,  45. 

Germ-plasm,  Weismann's  theory 
of,  5,  103,  173  ct  sct].\  immor- 
tality of,  9,  24  ;  continuity  of,  9, 
18,   49,   5^-67,  69-77,  72,   75, 


7S,  86  87,  104-105,  109-110, 
114,  120,  16S  ;  difterenees  in, 
12;  origin  of,  17;  indepen- 
dence of,  19  ;  and  natural  selec- 
tion, 21  ;  stnbility  of,  22,  49, 
57,66,  86-S9,  91-93,  99-100, 
104-105,  109,  112-114,  151 
et  scq. ;  lodged  in  nuckus,  29 ; 
and  ?omato-plasm,  29,  81,  no; 
the  modification  of,  36 ;  exami- 
nation of  Weismann's  theory  of, 
48  ;  Weismann's  theory  of  and 
Pangenesis,  52  ;  and  gemmules, 
.S2.  55,  58,  105-106,  121; 
multii)lication  of  in  the  general 
cellular  tissues  of  plants,  53; 
DeVrieson,  54;  Differentiation 
of,  55 ;  and  "  formative  ma- 
terial," 56 ;  and  stirp,  5S-59, 
61,  75,  106  ;  and  somatic-idio- 
plasm,  6(j ;  as  a  basis  of  heredity, 
70  ;  ancestral  germ-plasm,  1  23. 
Grafting,  and  the  effect  of  the 
somatic-tissues  on  the  germinal 
elements,  81 -8 2  ;  Darwin  on, 
83;  and  bud-variation,  98; 
Weismann  on,  126. 


H. 

Hackel,  theory  of  heredity,  2. 

Hartog,  Prof.  M.,  on  \\  ei^mnna 
155  ;  on  sexual  propagation, 
166-167. 

Healing  of  wounds,  34. 

Henslow,  Rev.  G.,  on  regenera- 
tion in  plants,  53. 

Heredity,  various  theories  of  2, 
49,  70;  statement  of  Weismann's 
theory  of,  17;  modification  of 
Weismann's  theory  of,  2"^,  46, 
52,  65,  68,  75,  163  et  sci]. ;  the 
nucleus  and,  29;  "carriers  of," 
32,  38,  70,  78,  122;  theory  of 
and  histology,  38  ;  examination 
of  Weismann's  theory  of,  48, 
105,  117;  compaiison  of  Weis- 
mann's, Darwin's,  and  Gallon's 
theories  of,  51,  105-106;  criti- 
cism of  Weismann'stheoiy  of  by 
.Strasburger,  51;  the  material 
basis  of,  61,  63. 


Index. 


219 


Hertwig,  O.,  theory  of  heredity,  2 ; 

on  polar  bodies,  46,  1 1^, 
Hildebrand,  or  effect  of  pollen 

upon    somatic    tissues  (Xenia), 

80  ;  on  Orchideae,  80. 
His,  theory  of  heredity,  2. 
Hoffmann,    on     the     inheritance 

of    acquired    characters,   93-4, 

114. 
Hydromedusaj,       VVeisniann     on 

generative    cells    o       71,    109; 

illustrate    continuity    of   germ- 
plasm,  72-73. 

I. 

Identicnl  twins,  41. 

Idi  plasm,  Nii^eli's  term,  31  ;  A 
and  Ij,  31-32  ;  sell-multiplica- 
tion of,  34 ;  amount  of  idio- 
plasm A  in  the  nucleus,  40. 

Ids,  123. 

Individual  differences,  VVeismann, 
39.  4^  43- 

Influence  of  a  previous  sire  upon 
the  progeny  of  the  same  dam, 
set  Telegony. 

Influence  of  external  conditions, 
see  Acquired  characters. 

Influence  of  pollen  upon  somatic 
tissues,  see  Xenia. 

Inheritance  of  acquired  characters, 
see  Acquired  characters. 

luveitebrates,  Weismann  on  sexual 
apjiaratus  of,  72,  74,  109. 


Jelly-fish,  regeneration  in,  4. 
Jordan,  on  mliei  iuiiice  of  ac(juired 
characters  ni  plants,  03. 

K. 

Karyokinesis,  37. 

L. 

Ijamarck,  Wei-.mnnn  and,  16,  21. 

Lamarekian  fiiclors,  importance 
o'.  .S7,  .S9>  62,  65,  O7,  69,  82, 
106   loH,  111-112,  I2,S,  147. 

Lile,  duration  of,  7,  10. 


M. 


Malingi6  Nouel,  on  Telegony, 
193  et  seq. 

Malva.  (Jdrtner  on,  80. 

Maupas,  on  the  Protozoa,  101, 
148. 

Metazoa  and  Metaphyta,  cause  of 
mortality  ol,  7,  24,  148;  rela- 
tion of  progeny  to  paienl>  in, 
16;  transmission  of  acijuiied 
characters  in,  i6 ;  propagaliin 
in,  51- 

Mivart,  on  inheritance  of  acquired 
characters,  94. 

Molecules,  54,  123. 

Morton,  Earl  of,  on  Telegony, 
192. 

Miiller,  Fritz,  on  bud  variation, 
95-. 

Multicellular  organisms,  see  Me- 
tazoa and  Metaphyla. 

N. 

Nageli,  theory  of  heredity,  2  ;  and 
idio-plasm,  31,  187  ;  and  germ- 
plasm,  36;  on  inheritance  of 
acquired  characters  in  plants, 
93- 

Natural  selection,  the  cau.se  of 
death,  8  ;  action  of,  20  ;  the 
material  for  the  operation  of, 
I3>  57  ;  uot  the  cause  of  sexual 
propagation,  13-14;  and  the 
i'rotozoa,  15,  loi  102  ;  and 
germ-plasm,  21  ;  sole  cause  of 
organic  evolution,  25,  59,  m, 
114. 

Nouel,  Malingi^-,  on  Telegony, 
1 9,',  ct  seq, 

Nucleo  plasm,  of  germ  and  soma- 
tic cells,  30. 

Nucleus,  alone  contains  germ- 
plasm,  29 ;  contains  two 
suiistances,  33 ;  and  heredity, 
37;  and  polar  bodies,  40; 
amount  of  idio  j)lasm  A  in,  40. 
Nutritive  congenital  changes,  64. 

o. 

Orchideae,  Ilildeband  on,  80. 
Organic   evolution,  the   cause  of. 


220 


Index. 


:i 


25  ;  Weismnnn's  theory  of,  26, 
4^,  50.  5^.  '^>^.  fiS,  '"^r.  100,  104, 
I06-I0S,  1 14-1 15,  147. 
Ova,  Weismann  on  the  size  of,  39. 


Pallas,  on  variability,  154. 

Pangenesis,  Darwin's  theory  of,  3, 
iU  ;  and  Weismann's  theory  of, 
52,  55.  71.  73.  12'  ;  and  i'an- 
mixia,  59-60  ;  Gallon  on,  60. 

Panmixia,  and  Pangenesis,  59-60. 

Parthcnogenetic  organisms,  and 
natural  selection,  15;  no  con- 
genital variations  in,  7-',  75. 

Parthenogenetic  ova,  Weismann 
on,  45,  89,  91,  109. 

Phylogenesis,  34. 

Physiological  isolation,  of  germ- 
oells,  74. 

Plants,  reproductive  cells  of,  74 ; 
intluence  of  polhn  upon  so- 
matic tissues  of  (^Xenia,  7S  So; 
bud-variation  in,  91,  94  99 ; 
Hoffmnnn's  inveslii;ations  on 
the  inheritance  of  accjuired  char- 
acters in,  93. 

Polar  bodies,  Weismann  on,  40 
46,  125;  examination  of  Wtis- 
manii's  explanation  of,  \i\ 
O.  Ilertwig  on,  46,  125. 

Protophyta,  natural  selection  and, 
114. 

Protozoa,  immortality  of,  7  ;  and 
natural  selection,  15,  114; 
origin  of  species  of,  15,  102; 
action  of  environment  on,  15; 
Maupas  on,  loi. 

R. 

Regeneration,  in  sea-anemones  and 
jelly-fish,  4,  35;  of  an  entire 
organism,  34 ;  Weismann  on, 
51  et  seq.  ;  in  Hegonia,  32; 
Rev.  (J.  Ilenslow  on,  53 ;  and 
stirp,  59. 

Rejuvenescence,  166. 

Representative  congenital  changes, 
65. 

Reproduction,   essential    meaning 


of  sexual,  8,  11  ;  in  the  Pro- 
tozoa, 16;  somatic.  35. 

Reproductive  elements,  potential 
immortality  of,  9  ;  of  Vertebrates 
and  Plants,  74. 

Reversion,  3,  91,  105. 

Roux,  on  the  principle  of  "strug- 
Klt:."  139- 

s. 

Sea-anemones,  regeneration  in,  4. 

Sexual  apparatus  of  Invertebrates. 
Weismann  on,  72,  74. 

Sexual-cells  and  somatic-cells,  75  - 
77,81,84. 

Sexual  propagation,  essential 
meaning  of,  8,  11,  87;  sole 
cause  of  congenital  variations, 
12,  S9-90,  102,  135,  141,  I^3, 
15S;  di<l  not  arise  tiuough  he 
agency  of  natural  seliction,  13- 
14;  in  multicellular  organisms, 
51  ;  Gnlton  on  the  origin  of, 
103;  in  CytisHS  adami,  127. 

Signil'icance  of  sexual  re|iroduction, 
sec  Sexual  Reproduction. 

3omatic-cells,  nucleo-plasm  of,  30; 
and  sexual  cells,  75-77,  81,  S^. 

Somatic-idio  jilasm,  32-33;  and 
germ-plasm,  69. 

Somatic  reproduction,  35,  52. 

Somato-plasm    and    germ-plasm. 

Specialized  congenital  changes,  65. 
Species,  Weismann  on  the  origin  of 

new,  100-101. 
Spencer,     Herbert,    theory    of 

heredity,  2  ;    on  Telegony,   191 

et  scij. 
Stability  of  germ-plasm,  j^^  Germ - 

plasm. 
Stirp,  and  gemmules,  5S-59,  61  ; 

andsonialic  tissues,  60;  and  the 

germinal  cells  of  llydromedusae, 

73;    and   germ-])Iasm,    75,   92, 

106,  133. 
Strasburger,      on      Weismann's 

theory  of  here<lity,  51  ;  on  the 

origin    of    sexual    propagation, 

167. 
Stylotitchia,  Maupas  on,  loi. 
Summary,  103. 


Index. 


221 


I'ro- 


T. 

Telegony,  77-79,  no,  141  et  scq., 
igi  et  scij. 

Tiansinissi',)ii  of  .ic<iuiie(l  char- 
acters, see  Ac(juirf(l  characters. 

Twins,  identical,  41. 

U. 

Unicellular  or<;anisins,  reproduc- 
tion of,  16;  action  ot  environ- 
ment on,  23,  147  ct  scq.  ;  poten- 
tially immortal,  23 ;  natural 
selection  and  the,  24,57,  114  5 
and  the  origin  of  hereditary  in- 
dividual variations,  100. 

V. 

Variation,  see  Congenital  varia- 
tions, Acquired  characters,  A:c.; 
Darwin  on  the  causes  of,  102; 
Weismann    on    the    origin    of, 

Veitebrates,  reproductive  cells  of, 

74- 
Vestigial    organs,  persistence    of, 

Vines,  Prof.  S,,  criticism  on 
Weismann,  14,  75,  90,  99,  152, 
178  ;  on  tile  Hasidioiiiycetes,  ijo. 

Vries,  De,  theory  of  heredity,  2  ; 
on  germ-plasm,  54 ;  on  the 
chromatophorcs  of  Algae,  83, 
111;  on  Xenia,  1 44. 

W. 

Weismann,  Prof.  August., 
theory  of  germ-plasm,  5,  17, 
173  et  scq.  ;  on  tlie  duration  of 
life, 7,  io;onllieessenti:d  nil  aning 
of  sexual  propagation,  11,  103, 
135,  141  ;  on  natural  selection 
as  the  origin  of  sexual  repro- 
duction, 14;  on  I'lof.  \  iiies' 
criticism,  14,  90,  i>9,  17S  et  seq.  ; 
on  the  Protozoa  and  natural  se- 
lection, 15,  102  ;  on  Lamarck, 
If) ;  on  adaptive  devclojiment, 
ii>;  and  natural  selection,  21; 
summary  of  tlieory  of  germ- 
plasm,    23 ;    theory    of  organic 


evolution,  26,  48,  50,  58,66,  68, 
87, 100,  104,  106-108, 114  115, 
147  ;  modilications  of  theory  of 
heredity,  2S,  46,  52,  65,  68,  75, 
163  ct  seq.;  and  of  self-mul- 
tiplical'on  of  idio-jjlasm,  34; 
on  "ontogenetic  grades,"  35, 
53  ;  on  the  modification  of  germ- 
plasm,  36;  on  chromatin,  38; 
on  iniii vidua!  differences,  39, 
41,  43  ;  on  the  size  of  ova, 
39  ;  on  polar  bodies,  40,  42,  46, 
125;  on  the  number  of  germ- 
cells,  44-4,s ;  on  jjarthenogenetic 
ova,  45,  89,  91  ;  examination 
of  his  theory  of  germ-))lasm  or 
heredity,  48,  8,;  ;  on  the  staliility 
and  Continuity  of  germ-plasm, 
49.  63,  66,  86-89,  91-93,  99- 
100,  103-105,  107,  109-110, 
I12-114,  120,  151,  158;  com- 
parison of  his  theory  with  those 
of  Darwin  and  Galton,  ,-1,  58; 
on  Strasburger's  critici-m  of  his 
theory,  52  ;  on  the  multiplication 
of  g:riii-plasin  in  the  general 
cellular  tissues  of  plants,  53; 
on  regeneration  in  plants,  53 ; 
anticii)ated  by  Galton,  59,  68; 
and  Galton,  63,  130  et  seq.\ 
on  transmi.ssion  of  acquired 
ciiaracters,  67,  83,  yfi,  n  i, 
127  ;  and  his  critics,  70;  on  the 
llydromediisae,  71,  109;  on  the 
sexual  apparatus  ot  Invertebrates, 
72  ;  and  the  inlluence  of  germ- 
cells  upon  sf)nialic  tissues  , 'lele- 
gony  and  Xenia),  8081,  i<j6 
et  seq. ;  and  the  signilicance 
of  grafting,  8i  82,  126;  and 
votigial  ciiaracters,  i)z;  on 
IKillmann's  invesligatiims,  93; 
on  bud-variation,  95,  97,  if>i; 
on  the  origin  of  henditary 
individual  variations,  loo-ioi  ; 
on  tlie  origin  of  new  species,  101. 
\\  ounds,  healing  of,  34. 

X. 

-Xenia,  78-^1,  uo,  141,  ij^^ctseq. 


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